From 7836559b774813bb8351dcb6246bef79242db679 Mon Sep 17 00:00:00 2001
From: highjune <highjune37@gmail.com>
Date: Sun, 28 May 2023 22:29:01 +0900
Subject: [PATCH 01/27] =?UTF-8?q?refactor(domain):=20step1=20=ED=94=BC?=
 =?UTF-8?q?=EB=93=9C=EB=B0=B1=20=EC=A0=81=EC=9A=A9?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

- Answer에서 setter 메서드 제거
- Answer에서 toString() 함수 제일 밑으로 이동
---
 src/main/java/nextstep/qna/domain/Answers.java  |  5 ++++-
 src/main/java/nextstep/qna/domain/Question.java | 16 ++++++----------
 2 files changed, 10 insertions(+), 11 deletions(-)

diff --git a/src/main/java/nextstep/qna/domain/Answers.java b/src/main/java/nextstep/qna/domain/Answers.java
index 5485ebc0e3..eb94d768d5 100644
--- a/src/main/java/nextstep/qna/domain/Answers.java
+++ b/src/main/java/nextstep/qna/domain/Answers.java
@@ -6,7 +6,6 @@
 import java.util.Objects;
 
 public class Answers implements Iterable<Answer> {
-
     private final List<Answer> answers;
 
     public Answers() {
@@ -24,6 +23,10 @@ public List<Answer> getAnswers() {
         return this.answers;
     }
 
+    public void deleteAnswers() {
+        answers.stream()
+                .forEach(answer -> answer.delete());
+    }
     @Override
     public Iterator<Answer> iterator() {
         return answers.iterator();
diff --git a/src/main/java/nextstep/qna/domain/Question.java b/src/main/java/nextstep/qna/domain/Question.java
index 51d98e8d5a..38923971b5 100644
--- a/src/main/java/nextstep/qna/domain/Question.java
+++ b/src/main/java/nextstep/qna/domain/Question.java
@@ -41,10 +41,6 @@ public void addAnswer(Answer answer) {
         answers.add(answer);
     }
 
-    private void setDeleted(boolean deleted) {
-        this.deleted = deleted;
-    }
-
     public boolean isDeleted() {
         return deleted;
     }
@@ -53,14 +49,9 @@ public List<Answer> getAnswers() {
         return answers.getAnswers();
     }
 
-    @Override
-    public String toString() {
-        return "Question [id=" + getId() + ", title=" + title + ", contents=" + contents + ", writer=" + writer + "]";
-    }
-
     public DeleteHistories delete(NsUser loginUser) {
         isSameUser(loginUser);
-        this.setDeleted(true);
+        this.deleted = true;
         return documentedDeleteHistories();
     }
 
@@ -78,4 +69,9 @@ private DeleteHistories documentedDeleteHistories() {
                 .forEach(answer -> deleteHistories.add(answer.delete()));
         return deleteHistories;
     }
+
+    @Override
+    public String toString() {
+        return "Question [id=" + getId() + ", title=" + title + ", contents=" + contents + ", writer=" + writer + "]";
+    }
 }

From 49789fb35522933b021ca120fd1bdf2ea7c4538d Mon Sep 17 00:00:00 2001
From: highjune <highjune37@gmail.com>
Date: Sun, 28 May 2023 22:46:55 +0900
Subject: [PATCH 02/27] =?UTF-8?q?refactor(domain):=20setter=EC=82=AD?=
 =?UTF-8?q?=EC=A0=9C,=20Answers=EC=97=90=20delete()=EC=B6=94=EA=B0=80?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 src/main/java/nextstep/qna/domain/Answer.java   |  2 +-
 src/main/java/nextstep/qna/domain/Answers.java  |  5 +++--
 src/main/java/nextstep/qna/domain/Question.java | 15 +++++----------
 3 files changed, 9 insertions(+), 13 deletions(-)

diff --git a/src/main/java/nextstep/qna/domain/Answer.java b/src/main/java/nextstep/qna/domain/Answer.java
index f6fff30f8d..a956d080ce 100644
--- a/src/main/java/nextstep/qna/domain/Answer.java
+++ b/src/main/java/nextstep/qna/domain/Answer.java
@@ -71,7 +71,7 @@ public String toString() {
 
     public DeleteHistory delete()  {
         isSameUser();
-        this.setDeleted(true);
+        this.deleted = true;
         return DeleteHistory.createAnswer(this.id, this.writer);
     }
 
diff --git a/src/main/java/nextstep/qna/domain/Answers.java b/src/main/java/nextstep/qna/domain/Answers.java
index eb94d768d5..2c52409a66 100644
--- a/src/main/java/nextstep/qna/domain/Answers.java
+++ b/src/main/java/nextstep/qna/domain/Answers.java
@@ -23,9 +23,10 @@ public List<Answer> getAnswers() {
         return this.answers;
     }
 
-    public void deleteAnswers() {
+    public DeleteHistories delete(DeleteHistories deleteHistories) {
         answers.stream()
-                .forEach(answer -> answer.delete());
+                .forEach(answer -> deleteHistories.add(answer.delete()));
+        return deleteHistories;
     }
     @Override
     public Iterator<Answer> iterator() {
diff --git a/src/main/java/nextstep/qna/domain/Question.java b/src/main/java/nextstep/qna/domain/Question.java
index 38923971b5..8522560b97 100644
--- a/src/main/java/nextstep/qna/domain/Question.java
+++ b/src/main/java/nextstep/qna/domain/Question.java
@@ -52,7 +52,11 @@ public List<Answer> getAnswers() {
     public DeleteHistories delete(NsUser loginUser) {
         isSameUser(loginUser);
         this.deleted = true;
-        return documentedDeleteHistories();
+
+        DeleteHistories deleteHistories = new DeleteHistories();
+        deleteHistories.add(DeleteHistory.createQuestion(this.id, this.writer));
+
+        return answers.delete(deleteHistories);
     }
 
     private void isSameUser(NsUser loginUser) {
@@ -61,15 +65,6 @@ private void isSameUser(NsUser loginUser) {
         }
     }
 
-    private DeleteHistories documentedDeleteHistories() {
-        DeleteHistories deleteHistories = new DeleteHistories();
-        deleteHistories.add(DeleteHistory.createQuestion(this.id, this.writer));
-
-        answers.getAnswers().stream()
-                .forEach(answer -> deleteHistories.add(answer.delete()));
-        return deleteHistories;
-    }
-
     @Override
     public String toString() {
         return "Question [id=" + getId() + ", title=" + title + ", contents=" + contents + ", writer=" + writer + "]";

From b4b0382742c31105303b22892b1197f09b824eb6 Mon Sep 17 00:00:00 2001
From: highjune <highjune37@gmail.com>
Date: Sun, 28 May 2023 23:28:48 +0900
Subject: [PATCH 03/27] =?UTF-8?q?refactor(domain):=20DeleteHistory?=
 =?UTF-8?q?=EC=97=90=EC=84=9C=20=EC=A0=95=EC=A0=81=20=ED=8C=A9=ED=86=A0?=
 =?UTF-8?q?=EB=A6=AC=20=EB=A9=94=EC=84=9C=EB=93=9C=EC=97=90=EC=84=9C=20?=
 =?UTF-8?q?=ED=8C=8C=EB=9D=BC=EB=AF=B8=ED=84=B0=20=EB=8F=84=EB=A9=94?=
 =?UTF-8?q?=EC=9D=B8=EC=9C=BC=EB=A1=9C=20=EB=B3=80=EA=B2=BD"?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 src/main/java/nextstep/qna/domain/Answer.java | 26 ++-----------------
 .../nextstep/qna/domain/DeleteHistory.java    |  8 +++---
 .../java/nextstep/qna/domain/Question.java    |  2 +-
 .../qna/domain/DeleteHistoriesTest.java       |  6 ++---
 4 files changed, 10 insertions(+), 32 deletions(-)

diff --git a/src/main/java/nextstep/qna/domain/Answer.java b/src/main/java/nextstep/qna/domain/Answer.java
index a956d080ce..e188d1fa80 100644
--- a/src/main/java/nextstep/qna/domain/Answer.java
+++ b/src/main/java/nextstep/qna/domain/Answer.java
@@ -72,7 +72,7 @@ public String toString() {
     public DeleteHistory delete()  {
         isSameUser();
         this.deleted = true;
-        return DeleteHistory.createAnswer(this.id, this.writer);
+        return DeleteHistory.createAnswer(this);
     }
 
     private void isSameUser() {
@@ -80,26 +80,4 @@ private void isSameUser() {
             throw new CannotDeleteException("다른 사람이 쓴 답변이 있어 삭제할 수 없습니다.");
         }
     }
-
-    @Override
-    public boolean equals(Object o) {
-        if (this == o) {
-            return true;
-        }
-        if (o == null || getClass() != o.getClass()) {
-            return false;
-        }
-        Answer answer = (Answer) o;
-        return isDeleted() == answer.isDeleted()
-                && Objects.equals(getId(), answer.getId())
-                && Objects.equals(getWriter(), answer.getWriter())
-                && Objects.equals(question, answer.question)
-                && Objects.equals(getContents(), answer.getContents())
-                && Objects.equals(createdDate, answer.createdDate);
-    }
-
-    @Override
-    public int hashCode() {
-        return Objects.hash(getId(), getWriter(), question, getContents(), isDeleted(), createdDate);
-    }
-}
+}
\ No newline at end of file
diff --git a/src/main/java/nextstep/qna/domain/DeleteHistory.java b/src/main/java/nextstep/qna/domain/DeleteHistory.java
index fb58b97e57..f6e28f215f 100644
--- a/src/main/java/nextstep/qna/domain/DeleteHistory.java
+++ b/src/main/java/nextstep/qna/domain/DeleteHistory.java
@@ -29,12 +29,12 @@ public DeleteHistory(ContentType contentType, Long contentId, NsUser deletedBy)
         this.deletedBy = deletedBy;
     }
 
-    public static DeleteHistory createAnswer(Long id, NsUser writer) {
-        return new DeleteHistory(ContentType.ANSWER, id, writer);
+    public static DeleteHistory createAnswer(Answer answer) {
+        return new DeleteHistory(ContentType.ANSWER, answer.getId(), answer.getWriter());
     }
 
-    public static DeleteHistory createQuestion(Long id, NsUser writer) {
-        return new DeleteHistory(ContentType.QUESTION, id, writer);
+    public static DeleteHistory createQuestion(Question question) {
+        return new DeleteHistory(ContentType.QUESTION, question.getId(), question.getWriter());
     }
 
     @Override
diff --git a/src/main/java/nextstep/qna/domain/Question.java b/src/main/java/nextstep/qna/domain/Question.java
index 8522560b97..7ddcce5aa3 100644
--- a/src/main/java/nextstep/qna/domain/Question.java
+++ b/src/main/java/nextstep/qna/domain/Question.java
@@ -54,7 +54,7 @@ public DeleteHistories delete(NsUser loginUser) {
         this.deleted = true;
 
         DeleteHistories deleteHistories = new DeleteHistories();
-        deleteHistories.add(DeleteHistory.createQuestion(this.id, this.writer));
+        deleteHistories.add(DeleteHistory.createQuestion(this));
 
         return answers.delete(deleteHistories);
     }
diff --git a/src/test/java/nextstep/qna/domain/DeleteHistoriesTest.java b/src/test/java/nextstep/qna/domain/DeleteHistoriesTest.java
index cbacaaa894..4ec15c617d 100644
--- a/src/test/java/nextstep/qna/domain/DeleteHistoriesTest.java
+++ b/src/test/java/nextstep/qna/domain/DeleteHistoriesTest.java
@@ -26,7 +26,7 @@ void setUp() {
     @DisplayName("Question을 추가했을 경우 Question에 대한 DeleteHistory를 만들어 리스트에 추가한다.")
     @Test
     void addQuestion_CreateDeleteHistory_And_AddDeleteHistorylist() {
-        deleteHistories.add(DeleteHistory.createQuestion(Q1.getId(), Q1.getWriter()));
+        deleteHistories.add(DeleteHistory.createQuestion(Q1));
         DeleteHistory deleteHistoryQ1 =
                 new DeleteHistory(ContentType.QUESTION, Q1.getId(), Q1.getWriter());
 
@@ -38,8 +38,8 @@ void addQuestion_CreateDeleteHistory_And_AddDeleteHistorylist() {
     @DisplayName("Answer를 추가했을 경우 Answer에 대한 DeleteHistory를 만들어 리스트에 추가한다.")
     @Test
     void addAnswer_CreateDeleteHistory_And_AddDeleteHistorylist() {
-        deleteHistories.add(DeleteHistory.createAnswer(A1.getId(), A1.getWriter()));
-        deleteHistories.add(DeleteHistory.createAnswer(A2.getId(), A2.getWriter()));
+        deleteHistories.add(DeleteHistory.createAnswer(A1));
+        deleteHistories.add(DeleteHistory.createAnswer(A2));
 
         DeleteHistory deleteHistoryA1 = new DeleteHistory(ContentType.ANSWER, A1.getId(), A1.getWriter());
         DeleteHistory deleteHistoryA2 = new DeleteHistory(ContentType.ANSWER, A2.getId(), A2.getWriter());

From 3d688c5749e11106f2bf8056a9b7b98a06ef4ee6 Mon Sep 17 00:00:00 2001
From: highjune <highjune37@gmail.com>
Date: Mon, 29 May 2023 00:21:20 +0900
Subject: [PATCH 04/27] =?UTF-8?q?docs(README.md):=20=EA=B8=B0=EB=8A=A5?=
 =?UTF-8?q?=EC=9A=94=EA=B5=AC=EC=82=AC=ED=95=AD=20=EC=9E=91=EC=84=B1?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 README.md | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/README.md b/README.md
index 069f3af51c..c98b501e5a 100644
--- a/README.md
+++ b/README.md
@@ -30,3 +30,32 @@
     - [x] question를 add 하면 question에 대한 DeleteHistory 를 만들어 리스트에 추가한다.
     - [x] answer을 add 하면 question에 대한 DeleteHistory를 만들어 리스트에 추가한다.
 
+
+## 수강신청 2단계(도메인 설계) 기능 목록
+### Student(학생)
+- [ ] 학생은 수강신청을 할 수 있다.
+- [ ] 수강 신청시 강의(Session)의 현재 수강 인원이 1 증가된다.
+- [ ] 수강신청시 최대 인원을 넘게 되면 예외를 던진다.
+- [ ] 수강 신청은 강의(Session) 의 상태가 `모집중` 일 때만 가능하다.
+  - [ ] `모집중`이 아닐 경우 예외를 던진다.
+
+### Course(과정)
+- [ ] 강의를 과정에 추가하고, 기수에 따라 강의를 조회할 수 있다.
+- [ ] 기수가 유효하지 않다면 (음수 or 초과 기수 조회) 예외를 던진다.
+
+### Session(강의)
+- [ ] 시작일과 종료일을 가진다.
+- [ ] 강의 커버 이미지 정보를 가진다.
+- type(타입)
+  - [ ] 무료, 유료 강의 2가지 값을 가진다(enum)
+- status(상태)
+  - [ ] 준비중, 모집중, 3가지를 가진다(enum)
+
+### 수강 신청 기능 요구사항
+- 과정(Course)은 기수 단위로 여러 개의 강의(Session)를 가질 수 있다.
+- 강의는 시작일과 종료일을 가진다.
+- 강의는 강의 커버 이미지 정보를 가진다.
+- 강의는 무료 강의와 유료 강의로 나뉜다.
+- 강의 상태는 준비중, 모집중, 종료 3가지 상태를 가진다.
+- 강의 수강신청은 강의 상태가 모집중일 때만 가능하다.
+- 강의는 강의 최대 수강 인원을 초과할 수 없다. 
\ No newline at end of file

From b39de98b9fcc76d5aaa060b09a4c8a523a5e5472 Mon Sep 17 00:00:00 2001
From: highjune <highjune37@gmail.com>
Date: Mon, 29 May 2023 00:34:30 +0900
Subject: [PATCH 05/27] =?UTF-8?q?test(domain):=20SessionTimeLineTest=20?=
 =?UTF-8?q?=ED=85=8C=EC=8A=A4=ED=8A=B8=20=EC=84=A0=EC=9E=91=EC=84=B1?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 .../courses/domain/SessionTimeLineTest.java   | 30 +++++++++++++++++++
 1 file changed, 30 insertions(+)
 create mode 100644 src/test/java/nextstep/courses/domain/SessionTimeLineTest.java

diff --git a/src/test/java/nextstep/courses/domain/SessionTimeLineTest.java b/src/test/java/nextstep/courses/domain/SessionTimeLineTest.java
new file mode 100644
index 0000000000..046ee4c538
--- /dev/null
+++ b/src/test/java/nextstep/courses/domain/SessionTimeLineTest.java
@@ -0,0 +1,30 @@
+package nextstep.courses.domain;
+
+import org.assertj.core.api.Assertions;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+
+import java.time.LocalDateTime;
+
+public class SessionTimeLineTest {
+
+    @Test
+    @DisplayName("강의 시작일이 강의 종료일보다 빠르면 예외를 던지지 않는다.")
+    void create_CreateAtBeforeThanClosedAt_NoException() {
+        LocalDateTime createAt = LocalDateTime.now();
+        LocalDateTime closeAt = createAt.plusDays(5);
+
+        Assertions.assertThatNoException()
+                .isThrownBy(() -> new SessionTimeLine(createAt, closeAt));
+    }
+
+    @Test
+    @DisplayName("강의 시작일이 강의 종료일보다 느리면 예외를 던진다.")
+    void create_CreateAtBeforeThanClosedAt_NoException() {
+        LocalDateTime createAt = LocalDateTime.now();
+        LocalDateTime closeAt = createAt.minusDays(5);
+
+        Assertions.assertThatNoException()
+                .isThrownBy(() -> new SessionTimeLine(createAt, closeAt));
+    }
+}

From 9c735e64860c51fe2a8656d03c8692dc6df16c9b Mon Sep 17 00:00:00 2001
From: highjune <highjune37@gmail.com>
Date: Mon, 29 May 2023 00:45:01 +0900
Subject: [PATCH 06/27] =?UTF-8?q?feat(domain):=20SessionTimeLine=20?=
 =?UTF-8?q?=EA=B0=9D=EC=B2=B4=20=EA=B5=AC=ED=98=84?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 .../courses/domain/SessionTimeLine.java       | 21 +++++++++++++++++++
 .../courses/domain/SessionTimeLineTest.java   |  4 ++--
 2 files changed, 23 insertions(+), 2 deletions(-)
 create mode 100644 src/main/java/nextstep/courses/domain/SessionTimeLine.java

diff --git a/src/main/java/nextstep/courses/domain/SessionTimeLine.java b/src/main/java/nextstep/courses/domain/SessionTimeLine.java
new file mode 100644
index 0000000000..95a5c976e4
--- /dev/null
+++ b/src/main/java/nextstep/courses/domain/SessionTimeLine.java
@@ -0,0 +1,21 @@
+package nextstep.courses.domain;
+
+import java.time.LocalDateTime;
+
+public class SessionTimeLine {
+
+    private LocalDateTime createAt;
+    private LocalDateTime closeAt;
+
+    public SessionTimeLine(LocalDateTime createAt, LocalDateTime closeAt) {
+        validateInterval(createAt, closeAt);
+        this.createAt = createAt;
+        this.closeAt = closeAt;
+    }
+
+    private void validateInterval(LocalDateTime createAt, LocalDateTime closeAt) {
+        if (closeAt.isBefore(createAt)) {
+            throw new IllegalArgumentException("강의 마감일이 시작일보다 빠를 수 없습니다.");
+        }
+    }
+}
diff --git a/src/test/java/nextstep/courses/domain/SessionTimeLineTest.java b/src/test/java/nextstep/courses/domain/SessionTimeLineTest.java
index 046ee4c538..3e9e4dbe0e 100644
--- a/src/test/java/nextstep/courses/domain/SessionTimeLineTest.java
+++ b/src/test/java/nextstep/courses/domain/SessionTimeLineTest.java
@@ -20,11 +20,11 @@ void create_CreateAtBeforeThanClosedAt_NoException() {
 
     @Test
     @DisplayName("강의 시작일이 강의 종료일보다 느리면 예외를 던진다.")
-    void create_CreateAtBeforeThanClosedAt_NoException() {
+    void create_CreateAtAfterThanClosedAt_NoException() {
         LocalDateTime createAt = LocalDateTime.now();
         LocalDateTime closeAt = createAt.minusDays(5);
 
-        Assertions.assertThatNoException()
+        Assertions.assertThatIllegalArgumentException()
                 .isThrownBy(() -> new SessionTimeLine(createAt, closeAt));
     }
 }

From 3d8a518e7e95e777874fbe11bce4215c24eaa087 Mon Sep 17 00:00:00 2001
From: highjune <highjune37@gmail.com>
Date: Mon, 29 May 2023 00:49:16 +0900
Subject: [PATCH 07/27] =?UTF-8?q?refactor(domain):=20SessionTimeLine=20?=
 =?UTF-8?q?=EB=82=A0=EC=A7=9C=20=EB=A1=9C=EC=A7=81=20=EC=B2=B4=ED=81=AC=20?=
 =?UTF-8?q?=EC=88=98=EC=A0=95?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 src/main/java/nextstep/courses/domain/SessionTimeLine.java | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/main/java/nextstep/courses/domain/SessionTimeLine.java b/src/main/java/nextstep/courses/domain/SessionTimeLine.java
index 95a5c976e4..bc4c785af5 100644
--- a/src/main/java/nextstep/courses/domain/SessionTimeLine.java
+++ b/src/main/java/nextstep/courses/domain/SessionTimeLine.java
@@ -14,8 +14,8 @@ public SessionTimeLine(LocalDateTime createAt, LocalDateTime closeAt) {
     }
 
     private void validateInterval(LocalDateTime createAt, LocalDateTime closeAt) {
-        if (closeAt.isBefore(createAt)) {
-            throw new IllegalArgumentException("강의 마감일이 시작일보다 빠를 수 없습니다.");
+        if (createAt.isAfter(closeAt)) {
+            throw new IllegalArgumentException("강의 시작일과 마감일을 잘못 입력하였습니다.");
         }
     }
 }

From 45b2955162409094ab6ebf2b91610df4bf8ca089 Mon Sep 17 00:00:00 2001
From: highjune <highjune37@gmail.com>
Date: Mon, 29 May 2023 01:14:55 +0900
Subject: [PATCH 08/27] =?UTF-8?q?feat(domain):=20SessionStatus=20Enum=20?=
 =?UTF-8?q?=EA=B0=9D=EC=B2=B4=20=EA=B5=AC=ED=98=84?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 README.md                                     |  4 ++--
 .../courses/domain/SessionStatus.java         | 20 +++++++++++++++++++
 2 files changed, 22 insertions(+), 2 deletions(-)
 create mode 100644 src/main/java/nextstep/courses/domain/SessionStatus.java

diff --git a/README.md b/README.md
index c98b501e5a..dea083b920 100644
--- a/README.md
+++ b/README.md
@@ -44,12 +44,12 @@
 - [ ] 기수가 유효하지 않다면 (음수 or 초과 기수 조회) 예외를 던진다.
 
 ### Session(강의)
-- [ ] 시작일과 종료일을 가진다.
+- [x] 시작일과 종료일을 가진다.
 - [ ] 강의 커버 이미지 정보를 가진다.
 - type(타입)
   - [ ] 무료, 유료 강의 2가지 값을 가진다(enum)
 - status(상태)
-  - [ ] 준비중, 모집중, 3가지를 가진다(enum)
+  - [ ] 준비중, 모집중, 종료 3가지를 가진다(enum)
 
 ### 수강 신청 기능 요구사항
 - 과정(Course)은 기수 단위로 여러 개의 강의(Session)를 가질 수 있다.
diff --git a/src/main/java/nextstep/courses/domain/SessionStatus.java b/src/main/java/nextstep/courses/domain/SessionStatus.java
new file mode 100644
index 0000000000..4b1fe92109
--- /dev/null
+++ b/src/main/java/nextstep/courses/domain/SessionStatus.java
@@ -0,0 +1,20 @@
+package nextstep.courses.domain;
+
+public enum SessionStatus {
+
+    READY("준비중"),
+    OPENED("모집중"),
+    CLSOED("종료")
+    ;
+
+    private String name;
+
+    SessionStatus(String name) {
+        this.name = name;
+    }
+
+    public boolean canJoin() {
+        return this.equals(OPENED);
+    }
+
+}

From 2e32239b235e9fa3747c1ecf595a5290174e166c Mon Sep 17 00:00:00 2001
From: highjune <highjune37@gmail.com>
Date: Mon, 29 May 2023 01:16:59 +0900
Subject: [PATCH 09/27] =?UTF-8?q?feat(domain):=20SessionType=20enum=20?=
 =?UTF-8?q?=EA=B0=9D=EC=B2=B4=20=EA=B5=AC=ED=98=84?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 README.md                                           |  4 ++--
 .../java/nextstep/courses/domain/SessionType.java   | 13 +++++++++++++
 2 files changed, 15 insertions(+), 2 deletions(-)
 create mode 100644 src/main/java/nextstep/courses/domain/SessionType.java

diff --git a/README.md b/README.md
index dea083b920..e7b48cc26b 100644
--- a/README.md
+++ b/README.md
@@ -47,9 +47,9 @@
 - [x] 시작일과 종료일을 가진다.
 - [ ] 강의 커버 이미지 정보를 가진다.
 - type(타입)
-  - [ ] 무료, 유료 강의 2가지 값을 가진다(enum)
+  - [x] 무료, 유료 강의 2가지 값을 가진다(enum)
 - status(상태)
-  - [ ] 준비중, 모집중, 종료 3가지를 가진다(enum)
+  - [x] 준비중, 모집중, 종료 3가지를 가진다(enum)
 
 ### 수강 신청 기능 요구사항
 - 과정(Course)은 기수 단위로 여러 개의 강의(Session)를 가질 수 있다.
diff --git a/src/main/java/nextstep/courses/domain/SessionType.java b/src/main/java/nextstep/courses/domain/SessionType.java
new file mode 100644
index 0000000000..b1aa2216bc
--- /dev/null
+++ b/src/main/java/nextstep/courses/domain/SessionType.java
@@ -0,0 +1,13 @@
+package nextstep.courses.domain;
+
+public enum SessionType {
+
+    FREE("무료"),
+    CHANGED("유료")
+    ;
+
+    private String name;
+    SessionType(String name) {
+        this.name = name;
+    }
+}

From 4e64f85651b1884fb12559fe0ab889d69e7a4f0b Mon Sep 17 00:00:00 2001
From: highjune <highjune37@gmail.com>
Date: Mon, 29 May 2023 01:22:03 +0900
Subject: [PATCH 10/27] =?UTF-8?q?feat(domain):=20SessionInfo=20=EA=B0=9D?=
 =?UTF-8?q?=EC=B2=B4=20=EA=B5=AC=ED=98=84?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 .../nextstep/courses/domain/SessionInfo.java   | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)
 create mode 100644 src/main/java/nextstep/courses/domain/SessionInfo.java

diff --git a/src/main/java/nextstep/courses/domain/SessionInfo.java b/src/main/java/nextstep/courses/domain/SessionInfo.java
new file mode 100644
index 0000000000..12f1ed1fd7
--- /dev/null
+++ b/src/main/java/nextstep/courses/domain/SessionInfo.java
@@ -0,0 +1,18 @@
+package nextstep.courses.domain;
+
+public class SessionInfo {
+
+    private final Long courseId;
+    private final Long ownerId;
+    private final String title;
+    private final String coverImageInfo;
+    private final SessionType sessionType;
+
+    public SessionInfo(Long courseId, Long ownerId, String title, String coverImageInfo, SessionType sessionType) {
+        this.courseId = courseId;
+        this.ownerId = ownerId;
+        this.title = title;
+        this.coverImageInfo = coverImageInfo;
+        this.sessionType = sessionType;
+    }
+}
\ No newline at end of file

From 08ac6b972291ed11bc6088d73dc9971fb465f158 Mon Sep 17 00:00:00 2001
From: highjune <highjune37@gmail.com>
Date: Mon, 29 May 2023 01:32:27 +0900
Subject: [PATCH 11/27] =?UTF-8?q?feat(domain):=20Session=20=EA=B0=9D?=
 =?UTF-8?q?=EC=B2=B4=20=EA=B5=AC=ED=98=84?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 .../java/nextstep/courses/domain/Session.java | 32 +++++++++++++++++++
 1 file changed, 32 insertions(+)
 create mode 100644 src/main/java/nextstep/courses/domain/Session.java

diff --git a/src/main/java/nextstep/courses/domain/Session.java b/src/main/java/nextstep/courses/domain/Session.java
new file mode 100644
index 0000000000..ae0b165537
--- /dev/null
+++ b/src/main/java/nextstep/courses/domain/Session.java
@@ -0,0 +1,32 @@
+package nextstep.courses.domain;
+
+import java.time.LocalDateTime;
+
+public class Session {
+
+
+    private final SessionInfo sessionInfo;
+    private final SessionStatus sessionStatus;
+    private final SessionTimeLine sessionTimeLine;
+    // Set<Student>
+    private final Long maxNumberOfStudent;
+
+    public Session(Long courseId, Long ownerId, String title, String coverImageInfo,
+                   SessionType sessionType, SessionStatus sessionStatus,
+                   LocalDateTime createdAt, LocalDateTime closedAt, Long maxNumOfStudent) {
+
+            this(new SessionInfo(courseId, ownerId, title, coverImageInfo, sessionType),
+                sessionStatus,
+                new SessionTimeLine(createdAt, closedAt),
+                maxNumOfStudent
+        );
+    }
+
+    public Session(SessionInfo sessionInfo, SessionStatus sessionStatus,
+                   SessionTimeLine sessionTimeLine, Long maxNumberOfStudent){
+        this.sessionInfo = sessionInfo;
+        this.sessionStatus = sessionStatus;
+        this.sessionTimeLine = sessionTimeLine;
+        this.maxNumberOfStudent = maxNumberOfStudent;
+    }
+}

From b516e7b94199573036a44ca55b1b8a0c5085966c Mon Sep 17 00:00:00 2001
From: highjune <highjune37@gmail.com>
Date: Mon, 29 May 2023 01:51:41 +0900
Subject: [PATCH 12/27] =?UTF-8?q?feat(domain):=20Student=20=EA=B0=9D?=
 =?UTF-8?q?=EC=B2=B4=20=EA=B5=AC=ED=98=84=20=EC=B6=94=EA=B0=80?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

- Session에 Set<Student> 추가
- StudentTest 위한SessionCreator 추가
- Student 객체 구현
---
 src/main/java/nextstep/courses/domain/Session.java |  4 +++-
 src/main/java/nextstep/courses/domain/Student.java | 12 ++++++++++++
 .../nextstep/courses/domain/SessionCreator.java    | 13 +++++++++++++
 .../java/nextstep/courses/domain/StudentTest.java  | 14 ++++++++++++++
 4 files changed, 42 insertions(+), 1 deletion(-)
 create mode 100644 src/main/java/nextstep/courses/domain/Student.java
 create mode 100644 src/test/java/nextstep/courses/domain/SessionCreator.java
 create mode 100644 src/test/java/nextstep/courses/domain/StudentTest.java

diff --git a/src/main/java/nextstep/courses/domain/Session.java b/src/main/java/nextstep/courses/domain/Session.java
index ae0b165537..c562193144 100644
--- a/src/main/java/nextstep/courses/domain/Session.java
+++ b/src/main/java/nextstep/courses/domain/Session.java
@@ -1,6 +1,8 @@
 package nextstep.courses.domain;
 
 import java.time.LocalDateTime;
+import java.util.HashSet;
+import java.util.Set;
 
 public class Session {
 
@@ -8,7 +10,7 @@ public class Session {
     private final SessionInfo sessionInfo;
     private final SessionStatus sessionStatus;
     private final SessionTimeLine sessionTimeLine;
-    // Set<Student>
+    private final Set<Student> students = new HashSet<>();
     private final Long maxNumberOfStudent;
 
     public Session(Long courseId, Long ownerId, String title, String coverImageInfo,
diff --git a/src/main/java/nextstep/courses/domain/Student.java b/src/main/java/nextstep/courses/domain/Student.java
new file mode 100644
index 0000000000..6dc8e2874d
--- /dev/null
+++ b/src/main/java/nextstep/courses/domain/Student.java
@@ -0,0 +1,12 @@
+package nextstep.courses.domain;
+
+public class Student {
+
+    private final Long studentId;
+    private final Long sessionId;
+
+    public Student(Long studentId, Long sessionId) {
+        this.studentId = studentId;
+        this.sessionId = sessionId;
+    }
+}
diff --git a/src/test/java/nextstep/courses/domain/SessionCreator.java b/src/test/java/nextstep/courses/domain/SessionCreator.java
new file mode 100644
index 0000000000..c2a2f23259
--- /dev/null
+++ b/src/test/java/nextstep/courses/domain/SessionCreator.java
@@ -0,0 +1,13 @@
+package nextstep.courses.domain;
+
+import java.time.LocalDateTime;
+
+public class SessionCreator {
+
+    public static Session create(Long maxNumberOfStudent, SessionStatus sessionStatus) {
+        SessionInfo sessionInfo = new SessionInfo(1L, 0L, "titleName",
+                "coverImage", SessionType.FREE);
+        SessionTimeLine sessionTimeLine = new SessionTimeLine(LocalDateTime.now(), LocalDateTime.now().plusDays(10));
+        return new Session(sessionInfo, sessionStatus, sessionTimeLine, maxNumberOfStudent);
+    }
+}
diff --git a/src/test/java/nextstep/courses/domain/StudentTest.java b/src/test/java/nextstep/courses/domain/StudentTest.java
new file mode 100644
index 0000000000..a876be5035
--- /dev/null
+++ b/src/test/java/nextstep/courses/domain/StudentTest.java
@@ -0,0 +1,14 @@
+package nextstep.courses.domain;
+
+import org.junit.jupiter.api.BeforeEach;
+
+public class StudentTest {
+
+    @BeforeEach
+    void setUp() {
+        Student june1 = new Student(0L, 10L);
+        Student june2 = new Student(0L, 10L);
+        Student june3 = new Student(0L, 10L);
+        Session session = SessionCreator.create(2L, SessionStatus.OPENED);
+    }
+}

From 6a684ead5ab5eb9293357059b8fb4e337368b544 Mon Sep 17 00:00:00 2001
From: highjune <highjune37@gmail.com>
Date: Mon, 29 May 2023 01:56:12 +0900
Subject: [PATCH 13/27] =?UTF-8?q?test(domain):=20StudentTest=20=EC=97=90?=
 =?UTF-8?q?=EC=84=9C=20=EB=93=B1=EB=A1=9D=EC=8B=9C=201=20=EC=A6=9D?=
 =?UTF-8?q?=EA=B0=80=ED=95=98=EB=8A=94=20=ED=85=8C=EC=8A=A4=ED=8A=B8=20?=
 =?UTF-8?q?=EB=A8=BC=EC=A0=80=20=EC=83=9D=EC=84=B1?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 .../nextstep/courses/domain/StudentTest.java  | 24 +++++++++++++++----
 1 file changed, 20 insertions(+), 4 deletions(-)

diff --git a/src/test/java/nextstep/courses/domain/StudentTest.java b/src/test/java/nextstep/courses/domain/StudentTest.java
index a876be5035..3fc7f1c41a 100644
--- a/src/test/java/nextstep/courses/domain/StudentTest.java
+++ b/src/test/java/nextstep/courses/domain/StudentTest.java
@@ -1,14 +1,30 @@
 package nextstep.courses.domain;
 
+import org.assertj.core.api.Assertions;
 import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
 
 public class StudentTest {
 
+    Student june1;
+    Student june2;
+    Student june3;
+    Session session;
+
     @BeforeEach
     void setUp() {
-        Student june1 = new Student(0L, 10L);
-        Student june2 = new Student(0L, 10L);
-        Student june3 = new Student(0L, 10L);
-        Session session = SessionCreator.create(2L, SessionStatus.OPENED);
+        june1 = new Student(0L, 10L);
+        june2 = new Student(0L, 10L);
+        june3 = new Student(0L, 10L);
+        session = SessionCreator.create(2L, SessionStatus.OPENED);
+    }
+
+    @Test
+    @DisplayName("학생은 수강신청시 강의의 현재 수강인원이 1이 증가한다.")
+    void enroll_SessionMaxNumberOfValue_PlusOne() {
+        june1.enroll(session);
+        Assertions.assertThat(session.totalStudentNum()).isEqualTo(1);
     }
+
 }

From 38cb914c952c896a14e22714ac8775e9906ebf56 Mon Sep 17 00:00:00 2001
From: highjune <highjune37@gmail.com>
Date: Mon, 29 May 2023 02:01:05 +0900
Subject: [PATCH 14/27] =?UTF-8?q?feat(domain):=20Student=20=EB=A5=BC=20Ses?=
 =?UTF-8?q?sion=EC=97=90=20=EB=93=B1=EB=A1=9D?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 src/main/java/nextstep/courses/domain/Session.java | 9 +++++++++
 src/main/java/nextstep/courses/domain/Student.java | 4 ++++
 2 files changed, 13 insertions(+)

diff --git a/src/main/java/nextstep/courses/domain/Session.java b/src/main/java/nextstep/courses/domain/Session.java
index c562193144..422d0ff452 100644
--- a/src/main/java/nextstep/courses/domain/Session.java
+++ b/src/main/java/nextstep/courses/domain/Session.java
@@ -31,4 +31,13 @@ public Session(SessionInfo sessionInfo, SessionStatus sessionStatus,
         this.sessionTimeLine = sessionTimeLine;
         this.maxNumberOfStudent = maxNumberOfStudent;
     }
+
+    public void add(Student student) {
+        // todo - validate
+        this.students.add(student);
+    }
+
+    public int totalStudentNum() {
+        return students.size();
+    }
 }
diff --git a/src/main/java/nextstep/courses/domain/Student.java b/src/main/java/nextstep/courses/domain/Student.java
index 6dc8e2874d..bf2dfe6944 100644
--- a/src/main/java/nextstep/courses/domain/Student.java
+++ b/src/main/java/nextstep/courses/domain/Student.java
@@ -9,4 +9,8 @@ public Student(Long studentId, Long sessionId) {
         this.studentId = studentId;
         this.sessionId = sessionId;
     }
+
+    public void enroll(Session session) {
+        session.add(this);
+    }
 }

From 944cd30b1b1d9f467b6f802d1ff9fc78aa2c4844 Mon Sep 17 00:00:00 2001
From: highjune <highjune37@gmail.com>
Date: Mon, 29 May 2023 02:08:23 +0900
Subject: [PATCH 15/27] =?UTF-8?q?feat(domain):=20=EC=88=98=EA=B0=95?=
 =?UTF-8?q?=EC=8B=A0=EC=B2=AD=EC=8B=9C=20=EC=9D=B8=EC=9B=90=20=EC=88=98=20?=
 =?UTF-8?q?=EC=B2=B4=ED=81=AC=20=EB=A1=9C=EC=A7=81?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

- 테스트 추가
- Student에 로직 추가
---
 .../courses/domain/CannotEnrollException.java     |  8 ++++++++
 .../java/nextstep/courses/domain/Session.java     |  5 ++++-
 .../java/nextstep/courses/domain/StudentTest.java | 15 ++++++++++++++-
 3 files changed, 26 insertions(+), 2 deletions(-)
 create mode 100644 src/main/java/nextstep/courses/domain/CannotEnrollException.java

diff --git a/src/main/java/nextstep/courses/domain/CannotEnrollException.java b/src/main/java/nextstep/courses/domain/CannotEnrollException.java
new file mode 100644
index 0000000000..17d709db99
--- /dev/null
+++ b/src/main/java/nextstep/courses/domain/CannotEnrollException.java
@@ -0,0 +1,8 @@
+package nextstep.courses.domain;
+
+public class CannotEnrollException extends RuntimeException{
+
+    public CannotEnrollException(String message) {
+        super(message);
+    }
+}
diff --git a/src/main/java/nextstep/courses/domain/Session.java b/src/main/java/nextstep/courses/domain/Session.java
index 422d0ff452..cba5dadeca 100644
--- a/src/main/java/nextstep/courses/domain/Session.java
+++ b/src/main/java/nextstep/courses/domain/Session.java
@@ -33,7 +33,10 @@ public Session(SessionInfo sessionInfo, SessionStatus sessionStatus,
     }
 
     public void add(Student student) {
-        // todo - validate
+        if (totalStudentNum() == maxNumberOfStudent) {
+            throw new CannotEnrollException(
+                    "현재 강의(Session)는 수강인원이 꽉 차서 더 이상 등록할 수 없습니다." + "최대인원 " + maxNumberOfStudent);
+        }
         this.students.add(student);
     }
 
diff --git a/src/test/java/nextstep/courses/domain/StudentTest.java b/src/test/java/nextstep/courses/domain/StudentTest.java
index 3fc7f1c41a..ce3280f210 100644
--- a/src/test/java/nextstep/courses/domain/StudentTest.java
+++ b/src/test/java/nextstep/courses/domain/StudentTest.java
@@ -5,6 +5,8 @@
 import org.junit.jupiter.api.DisplayName;
 import org.junit.jupiter.api.Test;
 
+import static org.assertj.core.api.Assertions.*;
+
 public class StudentTest {
 
     Student june1;
@@ -24,7 +26,18 @@ void setUp() {
     @DisplayName("학생은 수강신청시 강의의 현재 수강인원이 1이 증가한다.")
     void enroll_SessionMaxNumberOfValue_PlusOne() {
         june1.enroll(session);
-        Assertions.assertThat(session.totalStudentNum()).isEqualTo(1);
+        assertThat(session.totalStudentNum()).isEqualTo(1);
+    }
+
+    @Test
+    @DisplayName("학생은 수강신청시 강의의 최대 수강신청 인원을 넘을 경우 예외를 던진다.")
+    void enroll_OutOfMaxNumberOfStudent_ThrowException() {
+        session.add(june1);
+        session.add(june2);
+
+        assertThatThrownBy(() -> session.add(june3))
+                .isInstanceOf(CannotEnrollException.class)
+                .hasMessageContaining("현재 강의(Session)는 수강인원이 꽉 차서 더 이상 등록할 수 없습니다.");
     }
 
 }

From 25c83d2bb8fcecf70dc6c8b29bae09835342a4e7 Mon Sep 17 00:00:00 2001
From: highjune <highjune37@gmail.com>
Date: Mon, 29 May 2023 02:12:12 +0900
Subject: [PATCH 16/27] =?UTF-8?q?test(domain):=20=EC=88=98=EA=B0=95?=
 =?UTF-8?q?=EC=8B=A0=EC=B2=AD=EC=8B=9C=20=EC=B5=9C=EB=8C=80=20=EC=88=98?=
 =?UTF-8?q?=EA=B0=95=EC=9D=B8=EC=9B=90=20=EC=9D=B4=ED=95=98=EB=A9=B4=20?=
 =?UTF-8?q?=EC=98=88=EC=99=B8=20=EB=8D=98=EC=A7=80=EC=A7=80=20=EC=95=8A?=
 =?UTF-8?q?=EB=8A=94=EB=8B=A4?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 README.md                                            |  8 ++++----
 .../java/nextstep/courses/domain/StudentTest.java    | 12 +++++++++++-
 2 files changed, 15 insertions(+), 5 deletions(-)

diff --git a/README.md b/README.md
index e7b48cc26b..0035d05b07 100644
--- a/README.md
+++ b/README.md
@@ -33,9 +33,9 @@
 
 ## 수강신청 2단계(도메인 설계) 기능 목록
 ### Student(학생)
-- [ ] 학생은 수강신청을 할 수 있다.
-- [ ] 수강 신청시 강의(Session)의 현재 수강 인원이 1 증가된다.
-- [ ] 수강신청시 최대 인원을 넘게 되면 예외를 던진다.
+- [x] 학생은 수강신청을 할 수 있다.
+- [x] 수강 신청시 강의(Session)의 현재 수강 인원이 1 증가된다.
+- [x] 수강신청시 최대 인원을 넘게 되면 예외를 던진다.
 - [ ] 수강 신청은 강의(Session) 의 상태가 `모집중` 일 때만 가능하다.
   - [ ] `모집중`이 아닐 경우 예외를 던진다.
 
@@ -45,7 +45,7 @@
 
 ### Session(강의)
 - [x] 시작일과 종료일을 가진다.
-- [ ] 강의 커버 이미지 정보를 가진다.
+- [x] 강의 커버 이미지 정보를 가진다.
 - type(타입)
   - [x] 무료, 유료 강의 2가지 값을 가진다(enum)
 - status(상태)
diff --git a/src/test/java/nextstep/courses/domain/StudentTest.java b/src/test/java/nextstep/courses/domain/StudentTest.java
index ce3280f210..d2f6518a50 100644
--- a/src/test/java/nextstep/courses/domain/StudentTest.java
+++ b/src/test/java/nextstep/courses/domain/StudentTest.java
@@ -30,7 +30,7 @@ void enroll_SessionMaxNumberOfValue_PlusOne() {
     }
 
     @Test
-    @DisplayName("학생은 수강신청시 강의의 최대 수강신청 인원을 넘을 경우 예외를 던진다.")
+    @DisplayName("수강신청시 최대 수강신청 인원을 넘을 경우 예외를 던진다.")
     void enroll_OutOfMaxNumberOfStudent_ThrowException() {
         session.add(june1);
         session.add(june2);
@@ -40,4 +40,14 @@ void enroll_OutOfMaxNumberOfStudent_ThrowException() {
                 .hasMessageContaining("현재 강의(Session)는 수강인원이 꽉 차서 더 이상 등록할 수 없습니다.");
     }
 
+    @Test
+    @DisplayName("수강신청시 최대 수강인원을 넘지 않을 경우 예외를 던지지 않는다.")
+    void enroll_LessThanMaxNumberOfStudent_NoException() {
+        Session session = SessionCreator.create(5L, SessionStatus.READY);
+
+        assertThatNoException().isThrownBy(() -> session.add(june1));
+        assertThatNoException().isThrownBy(() -> session.add(june2));
+        assertThatNoException().isThrownBy(() -> session.add(june3));
+    }
+
 }

From 2f7a50230fa4881357bcf21e6598b4b604abb544 Mon Sep 17 00:00:00 2001
From: highjune <highjune37@gmail.com>
Date: Mon, 29 May 2023 02:23:16 +0900
Subject: [PATCH 17/27] =?UTF-8?q?test(domain):=20StudentTest=20=EA=B0=95?=
 =?UTF-8?q?=EC=9D=98=20=EC=83=81=ED=83=9C=EC=97=90=20=EB=94=B0=EB=A5=B8=20?=
 =?UTF-8?q?=ED=85=8C=EC=8A=A4=ED=8A=B8=20=EC=B6=94=EA=B0=80?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 .../java/nextstep/courses/domain/Session.java |  4 +++
 .../nextstep/courses/domain/StudentTest.java  | 30 ++++++++++++++++++-
 2 files changed, 33 insertions(+), 1 deletion(-)

diff --git a/src/main/java/nextstep/courses/domain/Session.java b/src/main/java/nextstep/courses/domain/Session.java
index cba5dadeca..c0c8710b2b 100644
--- a/src/main/java/nextstep/courses/domain/Session.java
+++ b/src/main/java/nextstep/courses/domain/Session.java
@@ -33,6 +33,10 @@ public Session(SessionInfo sessionInfo, SessionStatus sessionStatus,
     }
 
     public void add(Student student) {
+        if (!sessionStatus.canJoin()) {
+            throw new CannotEnrollException("현재는 수강신청을 할 수 없는 강의 상태입니다. 현재 강의 상태 = " + sessionStatus.name());
+        }
+
         if (totalStudentNum() == maxNumberOfStudent) {
             throw new CannotEnrollException(
                     "현재 강의(Session)는 수강인원이 꽉 차서 더 이상 등록할 수 없습니다." + "최대인원 " + maxNumberOfStudent);
diff --git a/src/test/java/nextstep/courses/domain/StudentTest.java b/src/test/java/nextstep/courses/domain/StudentTest.java
index d2f6518a50..5f1e06a38b 100644
--- a/src/test/java/nextstep/courses/domain/StudentTest.java
+++ b/src/test/java/nextstep/courses/domain/StudentTest.java
@@ -43,11 +43,39 @@ void enroll_OutOfMaxNumberOfStudent_ThrowException() {
     @Test
     @DisplayName("수강신청시 최대 수강인원을 넘지 않을 경우 예외를 던지지 않는다.")
     void enroll_LessThanMaxNumberOfStudent_NoException() {
-        Session session = SessionCreator.create(5L, SessionStatus.READY);
+        Session session = SessionCreator.create(3L, SessionStatus.OPENED);
 
         assertThatNoException().isThrownBy(() -> session.add(june1));
         assertThatNoException().isThrownBy(() -> session.add(june2));
         assertThatNoException().isThrownBy(() -> session.add(june3));
     }
 
+    @Test
+    @DisplayName("강의 상태(SessionStatus) '모집중'일 경우에 수강신청이 가능하다(예외를 던지지 않는다.")
+    void enroll_SessionStatus_OPENED_NoException() {
+        Session session = SessionCreator.create(3L, SessionStatus.OPENED);
+
+        assertThatNoException().isThrownBy(() -> session.add(june1));
+    }
+
+    @Test
+    @DisplayName("강의 상태(SessionStatus) '준비중'일 경우에 수깅신청시 예외를 던진다.")
+    void enroll_SessionStatus_READY_ThrowException() {
+        Session session = SessionCreator.create(3L, SessionStatus.READY);
+
+        assertThatThrownBy(() -> session.add(june1))
+                .isInstanceOf(CannotEnrollException.class);
+
+    }
+
+    @Test
+    @DisplayName("강의 상태(SessionStatus) '종료'일 경우에 수깅신청시 예외를 던진다.")
+    void enroll_SessionStatus_CLOSED_ThrowException() {
+        Session session = SessionCreator.create(3L, SessionStatus.CLSOED);
+
+        assertThatThrownBy(() -> session.add(june1))
+                .isInstanceOf(CannotEnrollException.class);
+    }
+
+
 }

From 0312ae04369c9e748f769f44523254a7ec9bfbe6 Mon Sep 17 00:00:00 2001
From: highjune <highjune37@gmail.com>
Date: Mon, 29 May 2023 02:27:57 +0900
Subject: [PATCH 18/27] =?UTF-8?q?feat(domain):=20StudentRepository=20?=
 =?UTF-8?q?=EC=B6=94=EA=B0=80?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 src/main/java/nextstep/courses/domain/Session.java     |  8 ++++++--
 .../nextstep/courses/domain/StudentRepository.java     | 10 ++++++++++
 2 files changed, 16 insertions(+), 2 deletions(-)
 create mode 100644 src/main/java/nextstep/courses/domain/StudentRepository.java

diff --git a/src/main/java/nextstep/courses/domain/Session.java b/src/main/java/nextstep/courses/domain/Session.java
index c0c8710b2b..66cf95c04e 100644
--- a/src/main/java/nextstep/courses/domain/Session.java
+++ b/src/main/java/nextstep/courses/domain/Session.java
@@ -37,9 +37,9 @@ public void add(Student student) {
             throw new CannotEnrollException("현재는 수강신청을 할 수 없는 강의 상태입니다. 현재 강의 상태 = " + sessionStatus.name());
         }
 
-        if (totalStudentNum() == maxNumberOfStudent) {
+        if (isPositionFull()) {
             throw new CannotEnrollException(
-                    "현재 강의(Session)는 수강인원이 꽉 차서 더 이상 등록할 수 없습니다." + "최대인원 " + maxNumberOfStudent);
+                    "현재 강의(Session)는 수강인원이 꽉 차서 더 이상 등록할 수 없습니다." + "최대인원 = " + maxNumberOfStudent);
         }
         this.students.add(student);
     }
@@ -47,4 +47,8 @@ public void add(Student student) {
     public int totalStudentNum() {
         return students.size();
     }
+
+    private boolean isPositionFull() {
+        return totalStudentNum() == maxNumberOfStudent;
+    }
 }
diff --git a/src/main/java/nextstep/courses/domain/StudentRepository.java b/src/main/java/nextstep/courses/domain/StudentRepository.java
new file mode 100644
index 0000000000..4e82e98a99
--- /dev/null
+++ b/src/main/java/nextstep/courses/domain/StudentRepository.java
@@ -0,0 +1,10 @@
+package nextstep.courses.domain;
+
+import java.util.List;
+
+public interface StudentRepository {
+
+    int save(Student student);
+
+    List<Student> findBySessionId(Long sessionId);
+}

From 9787ed51e6d3bfa35376f041e5222d857162889e Mon Sep 17 00:00:00 2001
From: highjune <highjune37@gmail.com>
Date: Mon, 29 May 2023 02:59:55 +0900
Subject: [PATCH 19/27] =?UTF-8?q?test(domain):=20=EA=B8=B0=EC=88=98?=
 =?UTF-8?q?=EC=97=90=20=EB=94=B0=EB=A5=B8=20=EA=B0=95=EC=9D=98=20=EC=A1=B0?=
 =?UTF-8?q?=ED=9A=8C=20=ED=85=8C=EC=8A=A4=ED=8A=B8=20&=20=ED=94=84?=
 =?UTF-8?q?=EB=A1=9C=EB=8D=95=EC=85=98=20=EC=BD=94=EB=93=9C=20=EC=B6=94?=
 =?UTF-8?q?=EA=B0=80?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 README.md                                     |  6 +--
 .../java/nextstep/courses/domain/Course.java  | 12 ++++++
 .../nextstep/courses/domain/CourseTest.java   | 43 +++++++++++++++++++
 3 files changed, 58 insertions(+), 3 deletions(-)
 create mode 100644 src/test/java/nextstep/courses/domain/CourseTest.java

diff --git a/README.md b/README.md
index 0035d05b07..e3b000406e 100644
--- a/README.md
+++ b/README.md
@@ -36,11 +36,11 @@
 - [x] 학생은 수강신청을 할 수 있다.
 - [x] 수강 신청시 강의(Session)의 현재 수강 인원이 1 증가된다.
 - [x] 수강신청시 최대 인원을 넘게 되면 예외를 던진다.
-- [ ] 수강 신청은 강의(Session) 의 상태가 `모집중` 일 때만 가능하다.
-  - [ ] `모집중`이 아닐 경우 예외를 던진다.
+- [x] 수강 신청은 강의(Session) 의 상태가 `모집중` 일 때만 가능하다.
+  - [x] `모집중`이 아닐 경우 예외를 던진다.
 
 ### Course(과정)
-- [ ] 강의를 과정에 추가하고, 기수에 따라 강의를 조회할 수 있다.
+- [x] 강의를 과정에 추가하고, 기수에 따라 강의를 조회할 수 있다.
 - [ ] 기수가 유효하지 않다면 (음수 or 초과 기수 조회) 예외를 던진다.
 
 ### Session(강의)
diff --git a/src/main/java/nextstep/courses/domain/Course.java b/src/main/java/nextstep/courses/domain/Course.java
index 0f69716043..cbfe3760fe 100644
--- a/src/main/java/nextstep/courses/domain/Course.java
+++ b/src/main/java/nextstep/courses/domain/Course.java
@@ -1,6 +1,8 @@
 package nextstep.courses.domain;
 
 import java.time.LocalDateTime;
+import java.util.ArrayList;
+import java.util.List;
 
 public class Course {
     private Long id;
@@ -9,6 +11,8 @@ public class Course {
 
     private Long creatorId;
 
+    private final List<Session> sessions = new ArrayList<>();
+
     private LocalDateTime createdAt;
 
     private LocalDateTime updatedAt;
@@ -40,6 +44,14 @@ public LocalDateTime getCreatedAt() {
         return createdAt;
     }
 
+    public Session getSession(int index) {
+        return this.sessions.get(index - 1);
+    }
+
+    public void addSession(Session session) {
+        this.sessions.add(session);
+    }
+
     @Override
     public String toString() {
         return "Course{" +
diff --git a/src/test/java/nextstep/courses/domain/CourseTest.java b/src/test/java/nextstep/courses/domain/CourseTest.java
new file mode 100644
index 0000000000..99046873ae
--- /dev/null
+++ b/src/test/java/nextstep/courses/domain/CourseTest.java
@@ -0,0 +1,43 @@
+package nextstep.courses.domain;
+
+import org.assertj.core.api.Assertions;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+
+import java.time.LocalDateTime;
+
+public class CourseTest {
+
+    private Course course;
+    private Session session1;
+    private Session session2;
+    private Session session3;
+
+    @BeforeEach
+    void setUp() {
+        this.course = new Course();
+        Long courseId = 1L;
+        SessionInfo sessionInfo = new SessionInfo(courseId, 1L, "titl1", "imageInfo", SessionType.FREE);
+        SessionStatus sessionStatus = SessionStatus.OPENED;
+        SessionTimeLine sessionTimeLine = new SessionTimeLine(LocalDateTime.now(), LocalDateTime.now().plusDays(10));
+
+        session1 = new Session(sessionInfo, sessionStatus, sessionTimeLine, 3L);
+        session2 = new Session(sessionInfo, sessionStatus, sessionTimeLine, 3L);
+        session3 = new Session(sessionInfo, sessionStatus, sessionTimeLine, 3L);
+
+        course.addSession(session1);
+        course.addSession(session2);
+        course.addSession(session3);
+    }
+
+    @Test
+    @DisplayName("기수에 따른 강의를 조회할 수 있다.")
+    void findCourse_DependOnId() {
+        Session session = course.getSession(1);
+
+        Assertions.assertThat(session).isEqualTo(this.session1);
+    }
+
+
+}

From 6f18763f7886cf88100cc6ba65b62dd5e28b1ed2 Mon Sep 17 00:00:00 2001
From: highjune <highjune37@gmail.com>
Date: Mon, 29 May 2023 03:11:21 +0900
Subject: [PATCH 20/27] =?UTF-8?q?test(domain):=20CourseTest=20=EC=A1=B4?=
 =?UTF-8?q?=EC=9E=AC=ED=95=98=EB=8A=94=20=EA=B0=95=EC=9D=98=20=EC=A1=B0?=
 =?UTF-8?q?=ED=9A=8C=20=ED=85=8C=EC=8A=A4=ED=8A=B8=20=EC=B6=94=EA=B0=80?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 .../java/nextstep/courses/domain/CourseTest.java   | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/src/test/java/nextstep/courses/domain/CourseTest.java b/src/test/java/nextstep/courses/domain/CourseTest.java
index 99046873ae..b6ccc180d2 100644
--- a/src/test/java/nextstep/courses/domain/CourseTest.java
+++ b/src/test/java/nextstep/courses/domain/CourseTest.java
@@ -4,6 +4,8 @@
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.DisplayName;
 import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.ValueSource;
 
 import java.time.LocalDateTime;
 
@@ -18,7 +20,7 @@ public class CourseTest {
     void setUp() {
         this.course = new Course();
         Long courseId = 1L;
-        SessionInfo sessionInfo = new SessionInfo(courseId, 1L, "titl1", "imageInfo", SessionType.FREE);
+        SessionInfo sessionInfo = new SessionInfo(courseId, 1L, "title1", "coverImageInfo", SessionType.FREE);
         SessionStatus sessionStatus = SessionStatus.OPENED;
         SessionTimeLine sessionTimeLine = new SessionTimeLine(LocalDateTime.now(), LocalDateTime.now().plusDays(10));
 
@@ -33,11 +35,19 @@ void setUp() {
 
     @Test
     @DisplayName("기수에 따른 강의를 조회할 수 있다.")
-    void findCourse_DependOnId() {
+    void findSession_FromCourse_ContainExactly() {
         Session session = course.getSession(1);
 
         Assertions.assertThat(session).isEqualTo(this.session1);
     }
 
+    @ParameterizedTest
+    @DisplayName("기수에 따른 존재하는 강의를 조회시 예외를 던지지 않는다.")
+    @ValueSource(ints = {1, 2, 3})
+    void findSession_FromCourseInExists_NoException(int value) {
+        Assertions.assertThatNoException()
+                .isThrownBy(() -> course.getSession(value));
+    }
+
 
 }

From 456423ee9d52213979f2cb4c12b49a9656d6ec87 Mon Sep 17 00:00:00 2001
From: highjune <highjune37@gmail.com>
Date: Mon, 29 May 2023 03:17:50 +0900
Subject: [PATCH 21/27] =?UTF-8?q?feat(domain):=20Course,=20CourseTest?=
 =?UTF-8?q?=EC=97=90=EC=84=9C=20=EC=9C=A0=ED=9A=A8=ED=95=98=EC=A7=80=20?=
 =?UTF-8?q?=EC=95=8A=EB=8A=94=20=EA=B8=B0=EC=88=98=20=EC=A1=B0=ED=9A=8C?=
 =?UTF-8?q?=EC=8B=9C=20=EC=98=88=EC=99=B8=EB=A5=BC=20=EB=8D=98=EC=A7=84?=
 =?UTF-8?q?=EB=8B=A4?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 .../java/nextstep/courses/domain/Course.java  | 11 +++++++++--
 .../nextstep/courses/domain/CourseTest.java   | 19 ++++++++++++++-----
 2 files changed, 23 insertions(+), 7 deletions(-)

diff --git a/src/main/java/nextstep/courses/domain/Course.java b/src/main/java/nextstep/courses/domain/Course.java
index cbfe3760fe..61c9fba089 100644
--- a/src/main/java/nextstep/courses/domain/Course.java
+++ b/src/main/java/nextstep/courses/domain/Course.java
@@ -44,14 +44,21 @@ public LocalDateTime getCreatedAt() {
         return createdAt;
     }
 
-    public Session getSession(int index) {
-        return this.sessions.get(index - 1);
+    public Session getSession(int generation) {
+        validateGeneration(generation);
+        return this.sessions.get(generation - 1);
     }
 
     public void addSession(Session session) {
         this.sessions.add(session);
     }
 
+    private void validateGeneration(int generation) {
+        if (generation <= 0) {
+            throw new IllegalArgumentException("기수는 1 기수 이상부터 시작합니다. 현재 기수 = " + generation);
+        }
+    }
+
     @Override
     public String toString() {
         return "Course{" +
diff --git a/src/test/java/nextstep/courses/domain/CourseTest.java b/src/test/java/nextstep/courses/domain/CourseTest.java
index b6ccc180d2..9272fa9df4 100644
--- a/src/test/java/nextstep/courses/domain/CourseTest.java
+++ b/src/test/java/nextstep/courses/domain/CourseTest.java
@@ -9,6 +9,8 @@
 
 import java.time.LocalDateTime;
 
+import static org.assertj.core.api.Assertions.*;
+
 public class CourseTest {
 
     private Course course;
@@ -38,16 +40,23 @@ void setUp() {
     void findSession_FromCourse_ContainExactly() {
         Session session = course.getSession(1);
 
-        Assertions.assertThat(session).isEqualTo(this.session1);
+        assertThat(session).isEqualTo(this.session1);
     }
 
     @ParameterizedTest
     @DisplayName("기수에 따른 존재하는 강의를 조회시 예외를 던지지 않는다.")
     @ValueSource(ints = {1, 2, 3})
-    void findSession_FromCourseInExists_NoException(int value) {
-        Assertions.assertThatNoException()
-                .isThrownBy(() -> course.getSession(value));
+    void findSession_FromCourseInExists_NoException(int generation) {
+        assertThatNoException()
+                .isThrownBy(() -> course.getSession(generation));
     }
 
-
+    @ParameterizedTest
+    @DisplayName("유효하지 않는 기수(음수, 0)를 조회시 예외를 발생한다.")
+    @ValueSource(ints = {-2, -1, 0})
+    void findSession_ByInvalidValue_ThrowException(int generation) {
+        assertThatIllegalArgumentException()
+                .isThrownBy(() -> course.getSession(generation))
+                .withMessageContaining("기수는 1 기수 이상부터 시작합니다.");
+    }
 }

From 65577c09d3deafd4fa44ef14f141175d0d252b15 Mon Sep 17 00:00:00 2001
From: highjune <highjune37@gmail.com>
Date: Mon, 29 May 2023 03:23:15 +0900
Subject: [PATCH 22/27] =?UTF-8?q?feat(domain):=20Course,=20CourseTest?=
 =?UTF-8?q?=EC=97=90=EC=84=9C=20=EC=9C=A0=ED=9A=A8=EC=84=B1=20=EC=B6=94?=
 =?UTF-8?q?=EA=B0=80?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 src/main/java/nextstep/courses/domain/Course.java   | 13 ++++++++++++-
 .../java/nextstep/courses/domain/CourseTest.java    | 11 ++++++++++-
 2 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/src/main/java/nextstep/courses/domain/Course.java b/src/main/java/nextstep/courses/domain/Course.java
index 61c9fba089..8c25e92ce7 100644
--- a/src/main/java/nextstep/courses/domain/Course.java
+++ b/src/main/java/nextstep/courses/domain/Course.java
@@ -54,8 +54,19 @@ public void addSession(Session session) {
     }
 
     private void validateGeneration(int generation) {
+        validateNegative(generation);
+        validateRange(generation);
+    }
+
+    private void validateNegative(int generation) {
         if (generation <= 0) {
-            throw new IllegalArgumentException("기수는 1 기수 이상부터 시작합니다. 현재 기수 = " + generation);
+            throw new IllegalArgumentException("기수는 1 기수 이상부터 시작합니다. 조회한 기수 = " + generation);
+        }
+    }
+
+    private void validateRange(int generation) {
+        if (sessions.size() < generation) {
+            throw new IllegalArgumentException("해당 기수의 강의는 존재하지 않습니다. 조회한 기수 = " + generation);
         }
     }
 
diff --git a/src/test/java/nextstep/courses/domain/CourseTest.java b/src/test/java/nextstep/courses/domain/CourseTest.java
index 9272fa9df4..160a266761 100644
--- a/src/test/java/nextstep/courses/domain/CourseTest.java
+++ b/src/test/java/nextstep/courses/domain/CourseTest.java
@@ -52,11 +52,20 @@ void findSession_FromCourseInExists_NoException(int generation) {
     }
 
     @ParameterizedTest
-    @DisplayName("유효하지 않는 기수(음수, 0)를 조회시 예외를 발생한다.")
+    @DisplayName("유효하지 않는 기수(음수, 0)를 조회시 예외를 던진다.")
     @ValueSource(ints = {-2, -1, 0})
     void findSession_ByInvalidValue_ThrowException(int generation) {
         assertThatIllegalArgumentException()
                 .isThrownBy(() -> course.getSession(generation))
                 .withMessageContaining("기수는 1 기수 이상부터 시작합니다.");
     }
+
+    @Test
+    @DisplayName("존재하지 않는 기수 강의를 조회시 예의를 던진다.")
+    void findSession_IfNotExists_ThrowException() {
+        assertThatIllegalArgumentException()
+                .isThrownBy(() -> course.getSession(4))
+                .withMessageContaining("해당 기수의 강의는 존재하지 않습니다.");
+
+    }
 }

From cefcc3e3ddd54002a76cde22d1dc396e81f01df5 Mon Sep 17 00:00:00 2001
From: highjune <highjune37@gmail.com>
Date: Mon, 29 May 2023 03:25:17 +0900
Subject: [PATCH 23/27] =?UTF-8?q?feat(domain):=20SessionRepository=20?=
 =?UTF-8?q?=EC=B6=94=EA=B0=80?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 src/main/java/nextstep/courses/domain/Course.java    |  1 +
 .../nextstep/courses/domain/SessionRepository.java   | 12 ++++++++++++
 2 files changed, 13 insertions(+)
 create mode 100644 src/main/java/nextstep/courses/domain/SessionRepository.java

diff --git a/src/main/java/nextstep/courses/domain/Course.java b/src/main/java/nextstep/courses/domain/Course.java
index 8c25e92ce7..ad58b93788 100644
--- a/src/main/java/nextstep/courses/domain/Course.java
+++ b/src/main/java/nextstep/courses/domain/Course.java
@@ -76,6 +76,7 @@ public String toString() {
                 "id=" + id +
                 ", title='" + title + '\'' +
                 ", creatorId=" + creatorId +
+                ", sessions=" + sessions +
                 ", createdAt=" + createdAt +
                 ", updatedAt=" + updatedAt +
                 '}';
diff --git a/src/main/java/nextstep/courses/domain/SessionRepository.java b/src/main/java/nextstep/courses/domain/SessionRepository.java
new file mode 100644
index 0000000000..2dcb8f48d6
--- /dev/null
+++ b/src/main/java/nextstep/courses/domain/SessionRepository.java
@@ -0,0 +1,12 @@
+package nextstep.courses.domain;
+
+import java.util.List;
+
+public interface SessionRepository {
+
+    int save(String session);
+
+    Session findById(Long id);
+
+    List<Session> findByCourseId(Long courseId);
+}

From 8058c79f7921773482675a840eceb05cbea8b342 Mon Sep 17 00:00:00 2001
From: highjune <highjune37@gmail.com>
Date: Mon, 29 May 2023 03:29:05 +0900
Subject: [PATCH 24/27] =?UTF-8?q?docs(README.md):=20Course=20=EC=B2=B4?=
 =?UTF-8?q?=ED=81=AC=EB=A6=AC=EC=8A=A4=ED=8A=B8=20=EC=97=85=EB=8D=B0?=
 =?UTF-8?q?=EC=9D=B4=ED=8A=B8?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 README.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/README.md b/README.md
index e3b000406e..9eec5cd0f7 100644
--- a/README.md
+++ b/README.md
@@ -41,7 +41,7 @@
 
 ### Course(과정)
 - [x] 강의를 과정에 추가하고, 기수에 따라 강의를 조회할 수 있다.
-- [ ] 기수가 유효하지 않다면 (음수 or 초과 기수 조회) 예외를 던진다.
+- [x] 기수가 유효하지 않다면 (음수 or 초과 기수 조회) 예외를 던진다.
 
 ### Session(강의)
 - [x] 시작일과 종료일을 가진다.

From aee8314d797d17f7f52df3f4b015e685b7911292 Mon Sep 17 00:00:00 2001
From: highjune <highjune37@gmail.com>
Date: Wed, 31 May 2023 22:06:31 +0900
Subject: [PATCH 25/27] =?UTF-8?q?feat(domain):=20Session=EC=97=90=20?=
 =?UTF-8?q?=EB=93=B1=EB=A1=9D=ED=95=98=EB=8A=94=20=EB=A9=94=EC=84=9C?=
 =?UTF-8?q?=EB=93=9C=EB=AA=85=20=EB=B3=80=EA=B2=BD?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

- add -> enroll
---
 .../java/nextstep/courses/domain/Session.java |  2 +-
 .../java/nextstep/courses/domain/Student.java |  2 +-
 .../nextstep/courses/domain/StudentTest.java  | 19 +++++++++----------
 3 files changed, 11 insertions(+), 12 deletions(-)

diff --git a/src/main/java/nextstep/courses/domain/Session.java b/src/main/java/nextstep/courses/domain/Session.java
index 66cf95c04e..0acd8c013b 100644
--- a/src/main/java/nextstep/courses/domain/Session.java
+++ b/src/main/java/nextstep/courses/domain/Session.java
@@ -32,7 +32,7 @@ public Session(SessionInfo sessionInfo, SessionStatus sessionStatus,
         this.maxNumberOfStudent = maxNumberOfStudent;
     }
 
-    public void add(Student student) {
+    public void enroll(Student student) {
         if (!sessionStatus.canJoin()) {
             throw new CannotEnrollException("현재는 수강신청을 할 수 없는 강의 상태입니다. 현재 강의 상태 = " + sessionStatus.name());
         }
diff --git a/src/main/java/nextstep/courses/domain/Student.java b/src/main/java/nextstep/courses/domain/Student.java
index bf2dfe6944..8b71cc4589 100644
--- a/src/main/java/nextstep/courses/domain/Student.java
+++ b/src/main/java/nextstep/courses/domain/Student.java
@@ -11,6 +11,6 @@ public Student(Long studentId, Long sessionId) {
     }
 
     public void enroll(Session session) {
-        session.add(this);
+        session.enroll(this);
     }
 }
diff --git a/src/test/java/nextstep/courses/domain/StudentTest.java b/src/test/java/nextstep/courses/domain/StudentTest.java
index 5f1e06a38b..1ff488b6f7 100644
--- a/src/test/java/nextstep/courses/domain/StudentTest.java
+++ b/src/test/java/nextstep/courses/domain/StudentTest.java
@@ -1,6 +1,5 @@
 package nextstep.courses.domain;
 
-import org.assertj.core.api.Assertions;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.DisplayName;
 import org.junit.jupiter.api.Test;
@@ -32,10 +31,10 @@ void enroll_SessionMaxNumberOfValue_PlusOne() {
     @Test
     @DisplayName("수강신청시 최대 수강신청 인원을 넘을 경우 예외를 던진다.")
     void enroll_OutOfMaxNumberOfStudent_ThrowException() {
-        session.add(june1);
-        session.add(june2);
+        session.enroll(june1);
+        session.enroll(june2);
 
-        assertThatThrownBy(() -> session.add(june3))
+        assertThatThrownBy(() -> session.enroll(june3))
                 .isInstanceOf(CannotEnrollException.class)
                 .hasMessageContaining("현재 강의(Session)는 수강인원이 꽉 차서 더 이상 등록할 수 없습니다.");
     }
@@ -45,9 +44,9 @@ void enroll_OutOfMaxNumberOfStudent_ThrowException() {
     void enroll_LessThanMaxNumberOfStudent_NoException() {
         Session session = SessionCreator.create(3L, SessionStatus.OPENED);
 
-        assertThatNoException().isThrownBy(() -> session.add(june1));
-        assertThatNoException().isThrownBy(() -> session.add(june2));
-        assertThatNoException().isThrownBy(() -> session.add(june3));
+        assertThatNoException().isThrownBy(() -> session.enroll(june1));
+        assertThatNoException().isThrownBy(() -> session.enroll(june2));
+        assertThatNoException().isThrownBy(() -> session.enroll(june3));
     }
 
     @Test
@@ -55,7 +54,7 @@ void enroll_LessThanMaxNumberOfStudent_NoException() {
     void enroll_SessionStatus_OPENED_NoException() {
         Session session = SessionCreator.create(3L, SessionStatus.OPENED);
 
-        assertThatNoException().isThrownBy(() -> session.add(june1));
+        assertThatNoException().isThrownBy(() -> session.enroll(june1));
     }
 
     @Test
@@ -63,7 +62,7 @@ void enroll_SessionStatus_OPENED_NoException() {
     void enroll_SessionStatus_READY_ThrowException() {
         Session session = SessionCreator.create(3L, SessionStatus.READY);
 
-        assertThatThrownBy(() -> session.add(june1))
+        assertThatThrownBy(() -> session.enroll(june1))
                 .isInstanceOf(CannotEnrollException.class);
 
     }
@@ -73,7 +72,7 @@ void enroll_SessionStatus_READY_ThrowException() {
     void enroll_SessionStatus_CLOSED_ThrowException() {
         Session session = SessionCreator.create(3L, SessionStatus.CLSOED);
 
-        assertThatThrownBy(() -> session.add(june1))
+        assertThatThrownBy(() -> session.enroll(june1))
                 .isInstanceOf(CannotEnrollException.class);
     }
 

From 39ad05a3bd581e426326b6891ce53dab5bb697b9 Mon Sep 17 00:00:00 2001
From: highjune <highjune37@gmail.com>
Date: Wed, 31 May 2023 23:17:50 +0900
Subject: [PATCH 26/27] =?UTF-8?q?feat(SessionEnrollment):=20=EA=B0=95?=
 =?UTF-8?q?=EC=9D=98=EB=93=B1=EB=A1=9D=20=EA=B0=9D=EC=B2=B4=20=EC=B6=94?=
 =?UTF-8?q?=EA=B0=80,=20=ED=85=8C=EC=8A=A4=ED=8A=B8=20=EC=B6=94=EA=B0=80?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

- SessionEnrollment 객체 구현 완료
- SessionEnrollmentTest 테스트 추가
- Session 에서 강의 등록에 관련 있는 3개의 멤버변수를 빼서 SessionEnrollment로 분리 완료
---
 .../java/nextstep/courses/domain/Session.java | 38 +++------
 .../courses/domain/SessionEnrollment.java     | 37 ++++++++
 .../nextstep/courses/domain/CourseTest.java   |  8 +-
 .../courses/domain/SessionCreator.java        |  3 +-
 .../courses/domain/SessionEnrollmentTest.java | 85 +++++++++++++++++++
 5 files changed, 139 insertions(+), 32 deletions(-)
 create mode 100644 src/main/java/nextstep/courses/domain/SessionEnrollment.java
 create mode 100644 src/test/java/nextstep/courses/domain/SessionEnrollmentTest.java

diff --git a/src/main/java/nextstep/courses/domain/Session.java b/src/main/java/nextstep/courses/domain/Session.java
index 0acd8c013b..aa3a6d7570 100644
--- a/src/main/java/nextstep/courses/domain/Session.java
+++ b/src/main/java/nextstep/courses/domain/Session.java
@@ -1,54 +1,38 @@
 package nextstep.courses.domain;
 
 import java.time.LocalDateTime;
-import java.util.HashSet;
-import java.util.Set;
 
 public class Session {
 
-
     private final SessionInfo sessionInfo;
-    private final SessionStatus sessionStatus;
+    private final SessionEnrollment sessionEnrollment;
     private final SessionTimeLine sessionTimeLine;
-    private final Set<Student> students = new HashSet<>();
-    private final Long maxNumberOfStudent;
 
     public Session(Long courseId, Long ownerId, String title, String coverImageInfo,
                    SessionType sessionType, SessionStatus sessionStatus,
                    LocalDateTime createdAt, LocalDateTime closedAt, Long maxNumOfStudent) {
 
             this(new SessionInfo(courseId, ownerId, title, coverImageInfo, sessionType),
-                sessionStatus,
-                new SessionTimeLine(createdAt, closedAt),
-                maxNumOfStudent
-        );
+                new SessionEnrollment(sessionStatus, maxNumOfStudent),
+                new SessionTimeLine(createdAt, closedAt));
     }
 
-    public Session(SessionInfo sessionInfo, SessionStatus sessionStatus,
-                   SessionTimeLine sessionTimeLine, Long maxNumberOfStudent){
+    public Session(SessionInfo sessionInfo, SessionEnrollment sessionEnrollment,
+                   SessionTimeLine sessionTimeLine){
         this.sessionInfo = sessionInfo;
-        this.sessionStatus = sessionStatus;
+        this.sessionEnrollment = sessionEnrollment;
         this.sessionTimeLine = sessionTimeLine;
-        this.maxNumberOfStudent = maxNumberOfStudent;
     }
 
     public void enroll(Student student) {
-        if (!sessionStatus.canJoin()) {
-            throw new CannotEnrollException("현재는 수강신청을 할 수 없는 강의 상태입니다. 현재 강의 상태 = " + sessionStatus.name());
-        }
-
-        if (isPositionFull()) {
-            throw new CannotEnrollException(
-                    "현재 강의(Session)는 수강인원이 꽉 차서 더 이상 등록할 수 없습니다." + "최대인원 = " + maxNumberOfStudent);
-        }
-        this.students.add(student);
+        sessionEnrollment.enroll(student);
     }
 
-    public int totalStudentNum() {
-        return students.size();
+    public Long totalStudentNum() {
+        return sessionEnrollment.totalStudentNum();
     }
 
-    private boolean isPositionFull() {
-        return totalStudentNum() == maxNumberOfStudent;
+    public boolean isPositionFull() {
+        return sessionEnrollment.isPositionFull();
     }
 }
diff --git a/src/main/java/nextstep/courses/domain/SessionEnrollment.java b/src/main/java/nextstep/courses/domain/SessionEnrollment.java
new file mode 100644
index 0000000000..aa60d4e9d2
--- /dev/null
+++ b/src/main/java/nextstep/courses/domain/SessionEnrollment.java
@@ -0,0 +1,37 @@
+package nextstep.courses.domain;
+
+import java.util.HashSet;
+import java.util.Set;
+
+public class SessionEnrollment {
+
+    private final SessionStatus sessionStatus;
+    private final Set<Student> students = new HashSet<>();
+    private final Long maxNumberOfStudent;
+
+    public SessionEnrollment(SessionStatus sessionStatus, Long maxNumberOfStudent) {
+        this.sessionStatus = sessionStatus;
+        this.maxNumberOfStudent = maxNumberOfStudent;
+    }
+
+    public void enroll(Student student) {
+        if (!sessionStatus.canJoin()) {
+            throw new CannotEnrollException("현재는 수강신청을 할 수 없는 강의 상태입니다. 현재 강의 상태 = " + sessionStatus.name());
+        }
+
+        if (isPositionFull()) {
+            throw new CannotEnrollException(
+                    "현재 강의(Session)는 수강인원이 꽉 차서 더 이상 등록할 수 없습니다." + "최대인원 = " + maxNumberOfStudent);
+        }
+        this.students.add(student);
+    }
+
+    public Long totalStudentNum() {
+        return Long.valueOf(students.size());
+    }
+
+    public boolean isPositionFull() {
+        return totalStudentNum() == maxNumberOfStudent;
+    }
+
+}
diff --git a/src/test/java/nextstep/courses/domain/CourseTest.java b/src/test/java/nextstep/courses/domain/CourseTest.java
index 160a266761..6a910d13bd 100644
--- a/src/test/java/nextstep/courses/domain/CourseTest.java
+++ b/src/test/java/nextstep/courses/domain/CourseTest.java
@@ -1,6 +1,5 @@
 package nextstep.courses.domain;
 
-import org.assertj.core.api.Assertions;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.DisplayName;
 import org.junit.jupiter.api.Test;
@@ -24,11 +23,12 @@ void setUp() {
         Long courseId = 1L;
         SessionInfo sessionInfo = new SessionInfo(courseId, 1L, "title1", "coverImageInfo", SessionType.FREE);
         SessionStatus sessionStatus = SessionStatus.OPENED;
+        SessionEnrollment sessionEnrollment = new SessionEnrollment(sessionStatus, 3L);
         SessionTimeLine sessionTimeLine = new SessionTimeLine(LocalDateTime.now(), LocalDateTime.now().plusDays(10));
 
-        session1 = new Session(sessionInfo, sessionStatus, sessionTimeLine, 3L);
-        session2 = new Session(sessionInfo, sessionStatus, sessionTimeLine, 3L);
-        session3 = new Session(sessionInfo, sessionStatus, sessionTimeLine, 3L);
+        session1 = new Session(sessionInfo, sessionEnrollment, sessionTimeLine);
+        session2 = new Session(sessionInfo, sessionEnrollment, sessionTimeLine);
+        session3 = new Session(sessionInfo, sessionEnrollment, sessionTimeLine);
 
         course.addSession(session1);
         course.addSession(session2);
diff --git a/src/test/java/nextstep/courses/domain/SessionCreator.java b/src/test/java/nextstep/courses/domain/SessionCreator.java
index c2a2f23259..b2f1a3c78c 100644
--- a/src/test/java/nextstep/courses/domain/SessionCreator.java
+++ b/src/test/java/nextstep/courses/domain/SessionCreator.java
@@ -7,7 +7,8 @@ public class SessionCreator {
     public static Session create(Long maxNumberOfStudent, SessionStatus sessionStatus) {
         SessionInfo sessionInfo = new SessionInfo(1L, 0L, "titleName",
                 "coverImage", SessionType.FREE);
+        SessionEnrollment sessionEnrollment = new SessionEnrollment(sessionStatus, maxNumberOfStudent);
         SessionTimeLine sessionTimeLine = new SessionTimeLine(LocalDateTime.now(), LocalDateTime.now().plusDays(10));
-        return new Session(sessionInfo, sessionStatus, sessionTimeLine, maxNumberOfStudent);
+        return new Session(sessionInfo, sessionEnrollment, sessionTimeLine);
     }
 }
diff --git a/src/test/java/nextstep/courses/domain/SessionEnrollmentTest.java b/src/test/java/nextstep/courses/domain/SessionEnrollmentTest.java
new file mode 100644
index 0000000000..b4ed46da18
--- /dev/null
+++ b/src/test/java/nextstep/courses/domain/SessionEnrollmentTest.java
@@ -0,0 +1,85 @@
+package nextstep.courses.domain;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.*;
+
+public class SessionEnrollmentTest {
+
+    Student june1;
+    Student june2;
+    Student june3;
+
+    @BeforeEach
+    void setUp() {
+        june1 = new Student(0L, 10L);
+        june2 = new Student(0L, 10L);
+        june3 = new Student(0L, 10L);
+    }
+
+    @Test
+    @DisplayName("학생은 수강신청시 강의의 현재 수강인원이 1이 증가한다.")
+    void enroll_SessionMaxNumberOfValue_PlusOne() {
+        SessionEnrollment sessionEnrollment =
+                new SessionEnrollment(SessionStatus.OPENED, 3l);
+
+        sessionEnrollment.enroll(june1);
+
+        assertThat(sessionEnrollment.totalStudentNum()).isEqualTo(1l);
+    }
+
+    @Test
+    @DisplayName("수강신청시 최대 수강신청 인원을 넘을 경우 예외를 던진다.")
+    void enroll_OutOfMaxNumberOfStudent_ThrowException() {
+        SessionEnrollment sessionEnrollment =
+                new SessionEnrollment(SessionStatus.OPENED, 0l);
+
+        assertThatThrownBy(() -> sessionEnrollment.enroll(june1))
+                .isInstanceOf(CannotEnrollException.class)
+                .hasMessageContaining("현재 강의(Session)는 수강인원이 꽉 차서 더 이상 등록할 수 없습니다.");
+    }
+
+    @Test
+    @DisplayName("수강신청시 최대 수강인원을 넘지 않을 경우 예외를 던지지 않는다.")
+    void enroll_LessThanMaxNumberOfStudent_NoException() {
+        SessionEnrollment sessionEnrollment =
+                new SessionEnrollment(SessionStatus.OPENED, 3l);
+
+        assertThatNoException().isThrownBy(() -> sessionEnrollment.enroll(june1));
+        assertThatNoException().isThrownBy(() -> sessionEnrollment.enroll(june2));
+        assertThatNoException().isThrownBy(() -> sessionEnrollment.enroll(june3));
+    }
+
+    @Test
+    @DisplayName("강의 상태(SessionStatus) '모집중'일 경우에 수강신청이 가능하다(예외를 던지지 않는다.")
+    void enroll_SessionStatus_OPENED_NoException() {
+        SessionEnrollment sessionEnrollment =
+                new SessionEnrollment(SessionStatus.OPENED, 3l);
+
+        assertThatNoException().isThrownBy(() -> sessionEnrollment.enroll(june1));
+    }
+
+    @Test
+    @DisplayName("강의 상태(SessionStatus) '준비중'일 경우에 수깅신청시 예외를 던진다.")
+    void enroll_SessionStatus_READY_ThrowException() {
+        SessionEnrollment sessionEnrollment =
+                new SessionEnrollment(SessionStatus.READY, 3l);
+
+        assertThatThrownBy(() -> sessionEnrollment.enroll(june1))
+                .isInstanceOf(CannotEnrollException.class)
+                .hasMessageContaining("현재는 수강신청을 할 수 없는 강의 상태입니다.");
+    }
+
+    @Test
+    @DisplayName("강의 상태(SessionStatus) '종료'일 경우에 수깅신청시 예외를 던진다.")
+    void enroll_SessionStatus_CLOSED_ThrowException() {
+        SessionEnrollment sessionEnrollment =
+                new SessionEnrollment(SessionStatus.CLSOED, 3l);
+
+        assertThatThrownBy(() -> sessionEnrollment.enroll(june1))
+                .isInstanceOf(CannotEnrollException.class)
+                .hasMessageContaining("현재는 수강신청을 할 수 없는 강의 상태입니다.");
+    }
+}
\ No newline at end of file

From 33d78896c9cc26198cfb4c7391adb679d6046840 Mon Sep 17 00:00:00 2001
From: highjune <highjune37@gmail.com>
Date: Thu, 1 Jun 2023 20:39:37 +0900
Subject: [PATCH 27/27] =?UTF-8?q?feat(domain):=20SessionEnrollment=20?=
 =?UTF-8?q?=EC=97=90=20=EC=9C=A0=ED=9A=A8=EC=84=B1=20=EC=B2=B4=ED=81=AC=20?=
 =?UTF-8?q?=EC=B6=94=EA=B0=80?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

- 이미 등록을 한 학생인 경우 예외를 던진다.
- README.md 추가
- AlreadyEnrollmentException 추가
- 테스트 추가
---
 README.md                                         | 11 +++++++++++
 .../domain/AlreadyEnrollmentException.java        |  8 ++++++++
 .../courses/domain/SessionEnrollment.java         | 14 +++++++++-----
 .../courses/domain/SessionEnrollmentTest.java     | 15 ++++++++++++++-
 4 files changed, 42 insertions(+), 6 deletions(-)
 create mode 100644 src/main/java/nextstep/courses/domain/AlreadyEnrollmentException.java

diff --git a/README.md b/README.md
index 9eec5cd0f7..c58093a8e5 100644
--- a/README.md
+++ b/README.md
@@ -51,6 +51,17 @@
 - status(상태)
   - [x] 준비중, 모집중, 종료 3가지를 가진다(enum)
 
+### SessionEnrollment(등록)
+- [x] 이미 등록을 한 학생은 예외를 던진다.
+- [x] 수용인원이 꽉 찬 강의에 등록시도를 할 경에 예외를 던진다.
+  - [x] 수강신청시 최대 수강인원을 넘지 않을 경우 예외를 던지지 않는다.
+- [x] 학생은 수강신청시 강의의 현재 수강인원이 1이 증가한다.
+- 강의 상태에 따라 등록상태가 다르다.
+  - [x] 강의 상태(SessionStatus) '모집중'일 경우에 수강신청이 가능하다(예외를 던지지 않는다)
+  - [x] 강의 상태(SessionStatus) '준비중'일 경우에 수깅신청시 예외를 던진다.
+  - [x] 강의 상태(SessionStatus) '종료'일 경우에 수깅신청시 예외를 던진다.
+
+
 ### 수강 신청 기능 요구사항
 - 과정(Course)은 기수 단위로 여러 개의 강의(Session)를 가질 수 있다.
 - 강의는 시작일과 종료일을 가진다.
diff --git a/src/main/java/nextstep/courses/domain/AlreadyEnrollmentException.java b/src/main/java/nextstep/courses/domain/AlreadyEnrollmentException.java
new file mode 100644
index 0000000000..117b58ecd4
--- /dev/null
+++ b/src/main/java/nextstep/courses/domain/AlreadyEnrollmentException.java
@@ -0,0 +1,8 @@
+package nextstep.courses.domain;
+
+public class AlreadyEnrollmentException extends RuntimeException{
+
+    public AlreadyEnrollmentException(String message) {
+        super(message);
+    }
+}
diff --git a/src/main/java/nextstep/courses/domain/SessionEnrollment.java b/src/main/java/nextstep/courses/domain/SessionEnrollment.java
index aa60d4e9d2..e9d7f9c26d 100644
--- a/src/main/java/nextstep/courses/domain/SessionEnrollment.java
+++ b/src/main/java/nextstep/courses/domain/SessionEnrollment.java
@@ -7,11 +7,11 @@ public class SessionEnrollment {
 
     private final SessionStatus sessionStatus;
     private final Set<Student> students = new HashSet<>();
-    private final Long maxNumberOfStudent;
+    private final Long capacity;
 
-    public SessionEnrollment(SessionStatus sessionStatus, Long maxNumberOfStudent) {
+    public SessionEnrollment(SessionStatus sessionStatus, Long capacity) {
         this.sessionStatus = sessionStatus;
-        this.maxNumberOfStudent = maxNumberOfStudent;
+        this.capacity = capacity;
     }
 
     public void enroll(Student student) {
@@ -21,7 +21,11 @@ public void enroll(Student student) {
 
         if (isPositionFull()) {
             throw new CannotEnrollException(
-                    "현재 강의(Session)는 수강인원이 꽉 차서 더 이상 등록할 수 없습니다." + "최대인원 = " + maxNumberOfStudent);
+                    "현재 강의(Session)는 수강인원이 꽉 차서 더 이상 등록할 수 없습니다." + "최대인원 = " + capacity);
+        }
+
+        if (students.contains(student)) {
+            throw new AlreadyEnrollmentException(student + " 학생은 이미 등록한 상태입니다.");
         }
         this.students.add(student);
     }
@@ -31,7 +35,7 @@ public Long totalStudentNum() {
     }
 
     public boolean isPositionFull() {
-        return totalStudentNum() == maxNumberOfStudent;
+        return totalStudentNum() == capacity;
     }
 
 }
diff --git a/src/test/java/nextstep/courses/domain/SessionEnrollmentTest.java b/src/test/java/nextstep/courses/domain/SessionEnrollmentTest.java
index b4ed46da18..a9e003271f 100644
--- a/src/test/java/nextstep/courses/domain/SessionEnrollmentTest.java
+++ b/src/test/java/nextstep/courses/domain/SessionEnrollmentTest.java
@@ -53,7 +53,7 @@ void enroll_LessThanMaxNumberOfStudent_NoException() {
     }
 
     @Test
-    @DisplayName("강의 상태(SessionStatus) '모집중'일 경우에 수강신청이 가능하다(예외를 던지지 않는다.")
+    @DisplayName("강의 상태(SessionStatus) '모집중'일 경우에 수강신청이 가능하다(예외를 던지지 않는다).")
     void enroll_SessionStatus_OPENED_NoException() {
         SessionEnrollment sessionEnrollment =
                 new SessionEnrollment(SessionStatus.OPENED, 3l);
@@ -82,4 +82,17 @@ void enroll_SessionStatus_CLOSED_ThrowException() {
                 .isInstanceOf(CannotEnrollException.class)
                 .hasMessageContaining("현재는 수강신청을 할 수 없는 강의 상태입니다.");
     }
+
+    @Test
+    @DisplayName("이미 등록된 학생의 경우 예외를 던진다.")
+    void enroll_AlreadyEnrollStudent_Duplicate_ThrowException() {
+        SessionEnrollment sessionEnrollment =
+                new SessionEnrollment(SessionStatus.OPENED, 3l);
+
+        sessionEnrollment.enroll(june1);
+
+        assertThatThrownBy(() -> sessionEnrollment.enroll(june1))
+                .isInstanceOf(AlreadyEnrollmentException.class)
+                .hasMessageContaining("학생은 이미 등록한 상태입니다.");
+    }
 }
\ No newline at end of file