diff --git a/src/test/java/study/StringTest.java b/src/test/java/study/StringTest.java
deleted file mode 100644
index 43e47d9..0000000
--- a/src/test/java/study/StringTest.java
+++ /dev/null
@@ -1,13 +0,0 @@
-package study;
-
-import org.junit.jupiter.api.Test;
-
-import static org.assertj.core.api.Assertions.assertThat;
-
-public class StringTest {
-    @Test
-    void replace() {
-        String actual = "abc".replace("b", "d");
-        assertThat(actual).isEqualTo("adc");
-    }
-}
diff --git a/src/test/java/study/mission0/SetTest.java b/src/test/java/study/mission0/SetTest.java
new file mode 100644
index 0000000..263de9d
--- /dev/null
+++ b/src/test/java/study/mission0/SetTest.java
@@ -0,0 +1,51 @@
+package study.mission0;
+
+
+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.CsvSource;
+import org.junit.jupiter.params.provider.ValueSource;
+
+import java.util.HashSet;
+import java.util.Set;
+
+import static org.assertj.core.api.AssertionsForClassTypes.assertThat;
+
+public class SetTest {
+    private Set<Integer> numbers;
+
+    @BeforeEach
+    void setUp(){
+        numbers = new HashSet<>();
+
+        numbers.add(1);
+        numbers.add(2);
+        numbers.add(3);
+    }
+
+
+    @Test
+    @DisplayName("요구사항 1: Set 의 크기를 확인한다.")
+    void checkSize(){
+        assertThat(numbers.size()).isEqualTo(4);
+    }
+
+
+    @ParameterizedTest
+    @ValueSource(ints = {1, 2, 3})
+    @DisplayName("요구사항 2: contains() 메소드를 활용해 값 존재하는지 확인하며 ParameterizedTest 를 이용해 중복코드를 제거한다.")
+    void isContainsNumber(int number){
+        assertThat(numbers.contains(number)).isTrue();
+    }
+
+
+    @ParameterizedTest
+    @CsvSource(value = {"1,true", "2,true", "3,true", "4,false", "5,false"})
+    @DisplayName("요구사항 3: contains() 메소드를 활용해 값 존재하는지 확인하며 입력값에 따라 true, false 를 반환한다.")
+    void isContains_expectedTrueOrFalse(int input, boolean expected){
+        assertThat(numbers.contains(input)).isEqualTo(expected);
+    }
+
+}
diff --git a/src/test/java/study/mission0/StringTest.java b/src/test/java/study/mission0/StringTest.java
new file mode 100644
index 0000000..cf9316b
--- /dev/null
+++ b/src/test/java/study/mission0/StringTest.java
@@ -0,0 +1,41 @@
+package study.mission0;
+
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+public class StringTest {
+    @Test
+    void replace() {
+        String actual = "abc".replace("b", "d");
+        assertThat(actual).isEqualTo("adc");
+    }
+
+
+    @Test
+    @DisplayName("요구사항 1 : split() 함수를 이용해 문자열을 분리시킨다.")
+    void split(){
+        String[] splitValues = "1,2".split(",");
+        assertThat(splitValues).contains("1");
+        assertThat(splitValues).containsExactly("1", "2"); // 원소가 정확히 일치하는지 확인
+    }
+
+
+    @Test
+    @DisplayName("요구사항 2 : substring() 함수를 이용해 괄호를 제거 시킨다.")
+    void substringParentheses(){
+        String value = "(1,2)";
+        String subValues = value.substring(1, value.length()-1);
+        assertThat(subValues).isEqualTo("1,2");
+    }
+
+
+    @Test
+    @DisplayName("요구사항 3 : chatAt() 메소드를 사용해 StringIndexOutOfBoundsException 을 발생시킨다.")
+    void chatAt_StringIndexOutOfBoundsException(){
+        String value = "abc";
+        assertThrows(StringIndexOutOfBoundsException.class, () -> value.charAt(value.length()+1));
+    }
+}