diff --git a/build.gradle b/build.gradle
index 8172fb7..d585e57 100644
--- a/build.gradle
+++ b/build.gradle
@@ -12,6 +12,8 @@ repositories {
 dependencies {
     testImplementation "org.junit.jupiter:junit-jupiter:5.7.2"
     testImplementation "org.assertj:assertj-core:3.19.0"
+    testImplementation 'org.mockito:mockito-core:4.11.0'
+
 }
 
 test {
diff --git a/src/main/java/BaseballApplication.java b/src/main/java/BaseballApplication.java
new file mode 100644
index 0000000..8f1f83d
--- /dev/null
+++ b/src/main/java/BaseballApplication.java
@@ -0,0 +1,19 @@
+import study.Baseball;
+import study.BaseballGame;
+import study.BaseballScanner;
+
+public class BaseballApplication {
+    public static void main(String[] args){
+        BaseballScanner scanner = new BaseballScanner();
+        Baseball baseball = new Baseball();
+        BaseballGame game = new BaseballGame(scanner, baseball);
+
+        do {
+            String result = game.playGame();
+            System.out.println(result);
+
+        } while(game.isReplay());
+
+        System.out.println(game.endGame());
+    }
+}
diff --git a/src/main/java/study/Baseball.java b/src/main/java/study/Baseball.java
new file mode 100644
index 0000000..c2c2a1d
--- /dev/null
+++ b/src/main/java/study/Baseball.java
@@ -0,0 +1,48 @@
+package study;
+
+import java.util.*;
+
+public class Baseball {
+    private final List<Integer> answerList;
+
+    public Baseball(){
+        answerList = getAnswer();
+    }
+
+    public Baseball(List<Integer> answerList) {
+        this.answerList = answerList;
+    }
+
+    public BaseballScore play(List<Integer> userInput){
+        BaseballScore score = new BaseballScore();
+
+        for (int i=0; i<userInput.size(); i++){
+            int index = answerList.indexOf(userInput.get(i));
+            score.addScore(index, i);
+        }
+
+        return score;
+    }
+
+    public List<Integer> getAnswer() {
+        List<Integer> answers = new ArrayList<>();
+        Random random = new Random();
+
+        while(answers.size() < 3){
+            int num = random.nextInt(9)+1;
+            answers = addUniqueNumber(num, answers);
+        }
+
+        return answers;
+
+    }
+
+    public List<Integer> addUniqueNumber(int num, List<Integer> answers){
+        if (!answers.contains(num)){
+            answers.add(num);
+        }
+
+        return answers;
+    }
+
+}
diff --git a/src/main/java/study/BaseballGame.java b/src/main/java/study/BaseballGame.java
new file mode 100644
index 0000000..72200e4
--- /dev/null
+++ b/src/main/java/study/BaseballGame.java
@@ -0,0 +1,39 @@
+package study;
+
+import study.messages.SuccessMessages;
+
+import java.util.List;
+
+public class BaseballGame {
+    private final BaseballScanner scanner;
+    private final Baseball baseball;
+
+    public BaseballGame(BaseballScanner scanner, Baseball baseball){
+        this.scanner = scanner;
+        this.baseball = baseball;
+    }
+
+    public String playGame(){
+        boolean collect = false;
+
+        while(!collect){
+            List<Integer> userInput = scanner.askNumbers();
+            BaseballScore score = baseball.play(userInput);
+
+            System.out.println(score.printScore());
+            collect = score.isThreeStrike();
+        }
+
+        return SuccessMessages.CORRECT_GAME;
+    }
+
+    public boolean isReplay(){
+        int input = scanner.askReplay();
+        return input != 2;
+    }
+
+    public String endGame(){
+        return SuccessMessages.END_GAME;
+    }
+
+}
diff --git a/src/main/java/study/BaseballScanner.java b/src/main/java/study/BaseballScanner.java
new file mode 100644
index 0000000..49ee2af
--- /dev/null
+++ b/src/main/java/study/BaseballScanner.java
@@ -0,0 +1,88 @@
+package study;
+
+import study.messages.ErrorMessages;
+
+import java.util.*;
+
+public class BaseballScanner {
+    private final Scanner scanner;
+
+    public BaseballScanner(){
+        this.scanner = new Scanner(System.in);
+    }
+
+    public List<Integer> askNumbers() {
+        System.out.println("숫자를 입력해 주세요 : ");
+        String input;
+
+        try{
+            input = checkLength(scanner.next());
+        } catch (NoSuchElementException ex){
+            throw new NoSuchElementException(ErrorMessages.INVALID_INPUT);
+        }
+
+        return convertList(input);
+    }
+
+    public int askReplay(){
+        System.out.println("게임을 새로 시작하려면 1, 종료하려면 2를 입력하세요.");
+        int input;
+
+        try{
+            input = validateOneOrTwo(scanner.nextInt());
+        } catch (NoSuchElementException ex){
+            throw new NoSuchElementException(ErrorMessages.INVALID_INPUT_REPLAY);
+        }
+
+        return input;
+
+    }
+
+    public String checkLength(String input){
+        input = input.replace(" ", "");
+
+        if (input.length() != 3){
+            throw new NoSuchElementException(ErrorMessages.INVALID_INPUT);
+        }
+        return input;
+    }
+
+    public int parseStringToInt(String str){
+        int result;
+
+        try{
+            result = Integer.parseInt(str);
+        } catch (NumberFormatException ex){
+            throw new NumberFormatException(ErrorMessages.INVALID_INPUT_NUMBER);
+        }
+
+        return result;
+    }
+
+
+    public List<Integer> convertList(String input){
+        List<Integer> numbers = new ArrayList<>();
+        String[] inputArr = input.split("");
+
+        for (String str: inputArr){
+            int number = parseStringToInt(str);
+            numbers.add(number);
+        }
+
+        return numbers;
+    }
+
+
+    public int validateOneOrTwo(int input){
+        if (input == 1 || input == 2){
+            return input;
+        }
+
+        throw new NoSuchElementException(ErrorMessages.INVALID_INPUT_REPLAY);
+    }
+
+
+    public void close(){
+        scanner.close();
+    }
+}
diff --git a/src/main/java/study/BaseballScore.java b/src/main/java/study/BaseballScore.java
new file mode 100644
index 0000000..1496acd
--- /dev/null
+++ b/src/main/java/study/BaseballScore.java
@@ -0,0 +1,61 @@
+package study;
+
+public class BaseballScore {
+    private int strikeCnt;
+    private int ballCnt;
+    private int nothingCnt;
+
+
+    public BaseballScore() {
+        this.strikeCnt = 0;
+        this.ballCnt = 0;
+        this.nothingCnt = 0;
+    }
+
+    public BaseballScore(int strikeCnt, int ballCnt, int nothingCnt) {
+        this.strikeCnt = strikeCnt;
+        this.ballCnt = ballCnt;
+        this.nothingCnt = nothingCnt;
+    }
+
+
+    public void addScore(int index, int i){
+        if (index == -1){
+            nothingCnt++;
+        } else if (index == i){
+            strikeCnt++;
+        } else if(index != i){
+            ballCnt++;
+        }
+    }
+
+    public boolean isThreeStrike(){
+        return strikeCnt == 3;
+    }
+
+    public String printScore(){
+        if(nothingCnt == 3) {
+            return "낫싱";
+        } else if (ballCnt != 0 && strikeCnt != 0){
+            return ballCnt + "볼 " + strikeCnt + "스트라이크";
+        } else if (ballCnt == 0 && strikeCnt != 0){
+            return strikeCnt + "스트라이크";
+        } else if(ballCnt != 0){
+            return ballCnt + "볼";
+        }
+
+        return "";
+    }
+
+    public int getStrikeCnt() {
+        return strikeCnt;
+    }
+
+    public int getBallCnt() {
+        return ballCnt;
+    }
+
+    public int getNothingCnt() {
+        return nothingCnt;
+    }
+}
diff --git a/src/main/java/study/messages/ErrorMessages.java b/src/main/java/study/messages/ErrorMessages.java
new file mode 100644
index 0000000..e38c0e2
--- /dev/null
+++ b/src/main/java/study/messages/ErrorMessages.java
@@ -0,0 +1,7 @@
+package study.messages;
+
+public class ErrorMessages {
+    public static final String INVALID_INPUT = "3자리 숫자를 입력해주세요.";
+    public static final String INVALID_INPUT_NUMBER = "숫자만 입력 가능합니다.";
+    public static final String INVALID_INPUT_REPLAY = "1 또는 2 숫자만 입력 가능합니다.";
+}
diff --git a/src/main/java/study/messages/SuccessMessages.java b/src/main/java/study/messages/SuccessMessages.java
new file mode 100644
index 0000000..d7e1918
--- /dev/null
+++ b/src/main/java/study/messages/SuccessMessages.java
@@ -0,0 +1,6 @@
+package study.messages;
+
+public class SuccessMessages {
+    public static final String CORRECT_GAME = "3개의 숫자를 모두 맞히셨습니다! 게임 종료";
+    public static final String END_GAME = "게임이 종료되었습니다.";
+}
diff --git a/src/test/java/study/BaseballGameTest.java b/src/test/java/study/BaseballGameTest.java
new file mode 100644
index 0000000..9ed50bf
--- /dev/null
+++ b/src/test/java/study/BaseballGameTest.java
@@ -0,0 +1,73 @@
+package study;
+
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+import study.messages.SuccessMessages;
+
+import java.util.Arrays;
+import java.util.List;
+
+import static org.junit.jupiter.api.Assertions.*;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+
+public class BaseballGameTest {
+
+    @Test
+    @DisplayName("playGame(): 3 스트라이크")
+    void playGame3Strike(){
+        // given
+        List<Integer> userInput = Arrays.asList(1, 2, 3);
+
+        BaseballScanner scanner = mock(BaseballScanner.class);
+        Baseball baseball = mock(Baseball.class);
+        BaseballGame game = new BaseballGame(scanner, baseball);
+
+        when(scanner.askNumbers()).thenReturn(userInput);
+        when(baseball.play(userInput)).thenReturn(new BaseballScore(3, 0, 0));
+
+
+        // when
+        String response = game.playGame();
+
+        // then
+        assertEquals(response, SuccessMessages.CORRECT_GAME);
+    }
+
+    @Test
+    @DisplayName("isReplayScanner(): 재게임 여부 1 입력으로 true 반환")
+    void isReplayInput1(){
+        // given
+        BaseballScanner scanner = mock(BaseballScanner.class);
+        Baseball baseball = mock(Baseball.class);
+        BaseballGame game = new BaseballGame(scanner, baseball);
+
+        when(scanner.askReplay()).thenReturn(1);
+
+        // when
+        boolean response = game.isReplay();
+
+        // then
+        assertTrue(response);
+    }
+
+    @Test
+    @DisplayName("isReplayScanner(): 재게임 여부 2 입력으로 false 반환")
+    void isReplayInput2(){
+        // given
+        BaseballScanner scanner = mock(BaseballScanner.class);
+        Baseball baseball = mock(Baseball.class);
+        BaseballGame game = new BaseballGame(scanner, baseball);
+
+        when(scanner.askReplay()).thenReturn(2);
+
+        // when
+        boolean response = game.isReplay();
+
+        // then
+        assertFalse(response);
+    }
+
+
+
+}
diff --git a/src/test/java/study/BaseballScannerTest.java b/src/test/java/study/BaseballScannerTest.java
new file mode 100644
index 0000000..259b3a5
--- /dev/null
+++ b/src/test/java/study/BaseballScannerTest.java
@@ -0,0 +1,301 @@
+package study;
+
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+import study.messages.ErrorMessages;
+
+import java.io.ByteArrayInputStream;
+import java.io.InputStream;
+import java.util.List;
+import java.util.NoSuchElementException;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+public class BaseballScannerTest {
+
+    // <scanner 테스트 하기 위해 System.setIn() 사용 시 주의할 점>
+    // System.in 에 대한 입력 스트림이 설정 되기 전에 scanner 가 초기화 되면 scanner 가 읽을 데이터가 없는 상태가 될 수 있음
+    // 특히 @BeforeEach 사용 시 System.in 설정 전에 먼저 객체가 생성되서 입력값이 없어서 예외 발생함
+
+    @Test
+    @DisplayName("askNumbers(): 사용자 입력 성공")
+    void askNumbers(){
+        // given
+        String input = "456";
+        InputStream in = new ByteArrayInputStream(input.getBytes());
+        System.setIn(in);
+
+        // when
+        BaseballScanner scanner = new BaseballScanner();
+        List<Integer> response = scanner.askNumbers();
+
+        // then
+        assertEquals(response.get(0), 4);
+        assertEquals(response.get(1), 5);
+        assertEquals(response.get(2), 6);
+    }
+
+    @Test
+    @DisplayName("askNumbers(): 공백이 포함된 숫자 입력으로 예외 발생")
+    void askNumbersContainEmpty_exception(){
+        // given
+        String input = "4 6";
+        InputStream in = new ByteArrayInputStream(input.getBytes());
+        System.setIn(in);
+
+        // when
+        BaseballScanner scanner = new BaseballScanner();
+        NoSuchElementException fail = assertThrows(NoSuchElementException.class, scanner::askNumbers);
+
+        // then
+        assertEquals(fail.getMessage(), ErrorMessages.INVALID_INPUT);
+    }
+
+    @Test
+    @DisplayName("askNumbers(): 숫자 3자리 이상을 입력으로 예외 발생")
+    void askNumbersInputOverSizeThree_exception(){
+        // given
+        String input = "123456";
+        InputStream in = new ByteArrayInputStream(input.getBytes());
+        System.setIn(in);
+
+        // when
+        BaseballScanner scanner = new BaseballScanner();
+        NoSuchElementException fail = assertThrows(NoSuchElementException.class, scanner::askNumbers);
+
+        // then
+        assertEquals(fail.getMessage(), ErrorMessages.INVALID_INPUT);
+    }
+
+    @Test
+    @DisplayName("askNumbers(): 문자열 입력으로 예외 발생")
+    void askNumbersInputString_exception(){
+        // given
+        String input = "문자열";
+        InputStream in = new ByteArrayInputStream(input.getBytes());
+        System.setIn(in);
+
+        // when
+        BaseballScanner scanner = new BaseballScanner();
+        NumberFormatException fail = assertThrows(NumberFormatException.class, scanner::askNumbers);
+
+        // then
+        assertEquals(fail.getMessage(), ErrorMessages.INVALID_INPUT_NUMBER);
+    }
+
+    @Test
+    @DisplayName("askNumbers(): 공백 입력으로 예외 발생")
+    void askNumbersInputEmpty_exception(){
+        // given
+        String input = " ";
+        InputStream in = new ByteArrayInputStream(input.getBytes());
+        System.setIn(in);
+
+        // when
+        BaseballScanner scanner = new BaseballScanner();
+        NoSuchElementException fail = assertThrows(NoSuchElementException.class, scanner::askNumbers);
+
+        // then
+        assertEquals(fail.getMessage(), ErrorMessages.INVALID_INPUT);
+    }
+
+
+    @Test
+    @DisplayName("askReplay(): 재게임 입력 성공")
+    void askReplay(){
+        // given
+        String input = "1";
+        InputStream in = new ByteArrayInputStream(input.getBytes());
+        System.setIn(in);
+
+        // when
+        BaseballScanner scanner = new BaseballScanner();
+        int response = scanner.askReplay();
+
+        // then
+        assertEquals(response, Integer.parseInt(input));
+    }
+
+    @Test
+    @DisplayName("askReplay(): 문자열 입력으로 예외 발생")
+    void askReplayInputString_exception(){
+        // given
+        String input = "문자열";
+        InputStream in = new ByteArrayInputStream(input.getBytes());
+        System.setIn(in);
+
+        // when
+        BaseballScanner scanner = new BaseballScanner();
+        NoSuchElementException fail = assertThrows(NoSuchElementException.class, scanner::askReplay);
+
+        // then
+        assertEquals(fail.getMessage(), ErrorMessages.INVALID_INPUT_REPLAY);
+    }
+
+
+    @Test
+    @DisplayName("askReplay(): 공백 입력으로 예외 발생")
+    void askReplayInputEmpty_exception(){
+        // given
+        String input = " ";
+        InputStream in = new ByteArrayInputStream(input.getBytes());
+        System.setIn(in);
+
+        // when
+        BaseballScanner scanner = new BaseballScanner();
+        NoSuchElementException fail = assertThrows(NoSuchElementException.class, scanner::askReplay);
+
+        // then
+        assertEquals(fail.getMessage(), ErrorMessages.INVALID_INPUT_REPLAY);
+    }
+
+    @Test
+    @DisplayName("askReplay(): 숫자 1 또는 2 이외의 숫자 입력으로 예외 발생")
+    void askReplayInputTwoNumber_exception(){
+        String input = "34";
+        InputStream in = new ByteArrayInputStream(input.getBytes());
+        System.setIn(in);
+
+        // when
+        BaseballScanner scanner = new BaseballScanner();
+        NoSuchElementException fail = assertThrows(NoSuchElementException.class, scanner::askReplay);
+
+        // then
+        assertEquals(fail.getMessage(), ErrorMessages.INVALID_INPUT_REPLAY);
+    }
+
+    
+    @Test
+    @DisplayName("checkLength(): 숫자 3자리 검증 성공")
+    void checkLength(){
+        // given
+        String input = "123";
+
+        // when
+        BaseballScanner scanner = new BaseballScanner();
+        String response = scanner.checkLength(input);
+
+        // then
+        assertEquals(response, input);
+    }
+
+    @Test
+    @DisplayName("checkLength(): 숫자 3자리 이상을 입력으로 예외 발생")
+    void checkLengthInputOverSizeThree_exception(){
+        // given
+        String input = "123456";
+
+        // when
+        BaseballScanner scanner = new BaseballScanner();
+        NoSuchElementException fail = assertThrows(NoSuchElementException.class, () -> scanner.checkLength(input));
+
+        // then
+        assertEquals(fail.getMessage(), ErrorMessages.INVALID_INPUT);
+    }
+
+    @Test
+    @DisplayName("parseStringToInt(): 문자열 숫자로 변환 성공")
+    void parseStringToInt(){
+        // given
+        String input = "123";
+
+        // when
+        BaseballScanner scanner = new BaseballScanner();
+        int response = scanner.parseStringToInt(input);
+
+        // then
+        assertEquals(response, 123);
+    }
+
+    @Test
+    @DisplayName("parseStringToInt(): 문자열 숫자 변환 실패로 예외 발생")
+    void parseInputString_exception(){
+        // given
+        String input = "문자열";
+
+        // when
+        BaseballScanner scanner = new BaseballScanner();
+        NumberFormatException fail = assertThrows(NumberFormatException.class, () -> scanner.parseStringToInt(input));
+
+        // then
+        assertEquals(fail.getMessage(), ErrorMessages.INVALID_INPUT_NUMBER);
+    }
+
+    @Test
+    @DisplayName("convertList(): 문자열을 숫자 리스트로 변환 성공")
+    void convertList(){
+        // given
+        String input = "123";
+
+        // when
+        BaseballScanner scanner = new BaseballScanner();
+        List<Integer> response = scanner.convertList(input);
+
+        // then
+        assertEquals(response.get(0), 1);
+        assertEquals(response.get(1), 2);
+        assertEquals(response.get(2), 3);
+    }
+
+
+
+    @Test
+    @DisplayName("convertList(): 문자열 숫자 리스트 변환 실패로 예외 발생")
+    void convertListInputString_exception(){
+        // given
+        String input = "문자열";
+
+        // when
+        BaseballScanner scanner = new BaseballScanner();
+        NumberFormatException fail = assertThrows(NumberFormatException.class, () -> scanner.convertList(input));
+
+        // then
+        assertEquals(fail.getMessage(), ErrorMessages.INVALID_INPUT_NUMBER);
+    }
+
+    @Test
+    @DisplayName("validateOneOrTwo(): 숫자 1 입력으로 성공")
+    void validateOneOrTwoInput1(){
+        // given
+        int input = 1;
+
+        // when
+        BaseballScanner scanner = new BaseballScanner();
+        int response = scanner.validateOneOrTwo(input);
+
+        // then
+        assertEquals(response, input);
+    }
+
+    @Test
+    @DisplayName("validateOneOrTwo(): 숫자 2 입력으로 성공")
+    void validateOneOrTwoInput2(){
+        // given
+        int input = 2;
+
+        // when
+        BaseballScanner scanner = new BaseballScanner();
+        int response = scanner.validateOneOrTwo(input);
+
+        // then
+        assertEquals(response, input);
+    }
+
+
+    @Test
+    @DisplayName("validateOneOrTwo(): 1이나 2가 아닌 숫자 입력으로 예외 발생")
+    void validateOneOrTwoInputEither1Or2_exception(){
+        // given
+        int input = 222;
+
+        // when
+        BaseballScanner scanner = new BaseballScanner();
+        NoSuchElementException fail = assertThrows(NoSuchElementException.class, () -> scanner.validateOneOrTwo(input));
+
+        // then
+        assertEquals(fail.getMessage(), ErrorMessages.INVALID_INPUT_REPLAY);
+    }
+
+
+}
diff --git a/src/test/java/study/BaseballScoreTest.java b/src/test/java/study/BaseballScoreTest.java
new file mode 100644
index 0000000..f1f28a3
--- /dev/null
+++ b/src/test/java/study/BaseballScoreTest.java
@@ -0,0 +1,179 @@
+package study;
+
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+public class BaseballScoreTest {
+
+    @Test
+    @DisplayName("addScore(): 스트라이크인 경우")
+    void addScoreStrike(){
+        // given
+        int index = 1;
+        int i = 1;
+
+        // when
+        BaseballScore score = new BaseballScore();
+        score.addScore(index, i);
+
+        // then
+        assertEquals(score.getBallCnt(), 0);
+        assertEquals(score.getStrikeCnt(), 1);
+        assertEquals(score.getNothingCnt(), 0);
+    }
+
+    @Test
+    @DisplayName("addScore(): 볼인 경우")
+    void addScoreBall(){
+        // given
+        int index = 2;
+        int i = 1;
+
+        // when
+        BaseballScore score = new BaseballScore();
+        score.addScore(index, i);
+
+        // then
+        assertEquals(score.getBallCnt(), 1);
+        assertEquals(score.getStrikeCnt(), 0);
+        assertEquals(score.getNothingCnt(), 0);
+    }
+
+    @Test
+    @DisplayName("addScore(): ball, strike 둘 다 아닌 경우")
+    void addScoreNothing(){
+        // given
+        int index = -1;
+        int i = 1;
+
+        // when
+        BaseballScore score = new BaseballScore();
+        score.addScore(index, i);
+
+        // then
+        assertEquals(score.getBallCnt(), 0);
+        assertEquals(score.getStrikeCnt(), 0);
+        assertEquals(score.getNothingCnt(), 1);
+    }
+
+    @Test
+    @DisplayName("isThreeStrike(): 3 스트라이크인 경우 true 반환")
+    void isThreeStrike(){
+        // given
+        BaseballScore score = new BaseballScore(3, 0, 0);
+
+        // when
+        boolean response = score.isThreeStrike();
+
+        // then
+        assertTrue(response);
+    }
+
+    @Test
+    @DisplayName("isThreeStrike(): 3 스트라이크 아닌 경우 false 반환")
+    void isNotThreeStrike(){
+        // given
+        BaseballScore score = new BaseballScore(1, 1, 1);
+
+        // when
+        boolean response = score.isThreeStrike();
+
+        // then
+        assertFalse(response);
+    }
+
+    @Test
+    @DisplayName("printScore(): 볼, 스트라이크 점수 출력")
+    void scorePrintBallAndStrike(){
+        // given
+        int ballCnt = 1;
+        int strikeCnt = 2;
+        int nothingCnt = 0;
+
+        BaseballScore score = new BaseballScore(strikeCnt, ballCnt, nothingCnt);
+
+        // when
+        String response = score.printScore();
+
+        // then
+        assertEquals(response, ballCnt + "볼 " + strikeCnt + "스트라이크");
+
+    }
+
+    @Test
+    @DisplayName("printScore(): 3 스트라이크 점수 출력")
+    void scorePrint3Strike(){
+        // given
+        int ballCnt = 0;
+        int strikeCnt = 3;
+        int nothingCnt = 0;
+
+        BaseballScore score = new BaseballScore(strikeCnt, ballCnt, nothingCnt);
+
+        // when
+        String response = score.printScore();
+
+        // then
+        assertEquals(response,  strikeCnt + "스트라이크");
+
+    }
+
+    @Test
+    @DisplayName("printScore(): 스트라이크 점수 출력")
+    void scorePrintStrike(){
+        // given
+        int ballCnt = 0;
+        int strikeCnt = 2;
+        int nothingCnt = 0;
+
+        BaseballScore score = new BaseballScore(strikeCnt, ballCnt, nothingCnt);
+
+        // when
+        String response = score.printScore();
+
+        // then
+        assertEquals(response,  strikeCnt + "스트라이크");
+
+    }
+
+    @Test
+    @DisplayName("printScore(): 볼 점수 출력")
+    void scorePrintBall(){
+        // given
+        int ballCnt = 2;
+        int strikeCnt = 0;
+        int nothingCnt = 1;
+
+        BaseballScore score = new BaseballScore(strikeCnt, ballCnt, nothingCnt);
+
+        // when
+        String response = score.printScore();
+
+        // then
+        assertEquals(response, ballCnt + "볼");
+
+    }
+
+
+    @Test
+    @DisplayName("printScore(): 낫싱 점수 출력")
+    void scorePrintNothing(){
+        // given
+        int ballCnt = 0;
+        int strikeCnt = 0;
+        int nothingCnt = 3;
+
+        BaseballScore score = new BaseballScore(strikeCnt, ballCnt, nothingCnt);
+
+        // when
+        String response = score.printScore();
+
+        // then
+        assertEquals(response, "낫싱");
+
+    }
+
+
+}
diff --git a/src/test/java/study/BaseballTest.java b/src/test/java/study/BaseballTest.java
new file mode 100644
index 0000000..900f543
--- /dev/null
+++ b/src/test/java/study/BaseballTest.java
@@ -0,0 +1,151 @@
+package study;
+
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.RepeatedTest;
+import org.junit.jupiter.api.Test;
+import org.mockito.Mock;
+import org.mockito.Mockito;
+
+import java.io.ByteArrayInputStream;
+import java.io.InputStream;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+
+import static org.junit.jupiter.api.Assertions.*;
+import static org.mockito.Mockito.when;
+
+public class BaseballTest {
+
+    @Test
+    @DisplayName("play(): 3 스트라이크")
+    void play3Strike(){
+        // given
+        List<Integer> inputList = Arrays.asList(3, 5, 6);
+        List<Integer> answerList = Arrays.asList(3, 5, 6);
+
+        // when
+        Baseball baseball = new Baseball(answerList);
+        BaseballScore response = baseball.play(inputList);
+
+        // then
+        assertEquals(response.getStrikeCnt(), 3);
+        assertEquals(response.getBallCnt(), 0);
+        assertEquals(response.getNothingCnt(), 0);
+    }
+
+    @Test
+    @DisplayName("play(): 1 스트라이크 2볼")
+    void play1Strike2Ball(){
+        // given
+        List<Integer> inputList = Arrays.asList(3, 5, 6);
+        List<Integer> answerList = Arrays.asList(3, 6, 5);
+
+        // when
+        Baseball baseball = new Baseball(answerList);
+        BaseballScore response = baseball.play(inputList);
+
+        // then
+        assertEquals(response.getStrikeCnt(), 1);
+        assertEquals(response.getBallCnt(), 2);
+        assertEquals(response.getNothingCnt(), 0);
+    }
+
+    @Test
+    @DisplayName("play(): 3볼")
+    void play3Ball(){
+        // given
+        List<Integer> inputList = Arrays.asList(3, 5, 6);
+        List<Integer> answerList = Arrays.asList(5, 6, 3);
+
+
+        // when
+        Baseball baseball = new Baseball(answerList);
+        BaseballScore response = baseball.play(inputList);
+
+        // then
+        assertEquals(response.getStrikeCnt(), 0);
+        assertEquals(response.getBallCnt(), 3);
+        assertEquals(response.getNothingCnt(), 0);
+
+    }
+
+    @Test
+    @DisplayName("play(): 낫싱")
+    void playNothing(){
+        // given
+        List<Integer> inputList = Arrays.asList(3, 5, 6);
+        List<Integer> answerList = Arrays.asList(7, 8, 9);
+
+
+        // when
+        Baseball baseball = new Baseball(answerList);
+        BaseballScore response = baseball.play(inputList);
+
+
+        // then
+        assertEquals(response.getStrikeCnt(), 0);
+        assertEquals(response.getBallCnt(), 0);
+        assertEquals(response.getNothingCnt(), 3);
+
+    }
+
+
+    @RepeatedTest(10) // 10번 반복 테스트
+    @DisplayName("getAnswer() 성공: 랜덤 3자리 수 생성")
+    void getAnswer(){
+        // given
+        // when
+        Baseball baseball = new Baseball();
+        List<Integer> response = baseball.getAnswer();
+
+        // then
+        assertEquals(response.size(), 3);
+        assertNotNull(response.get(0));
+        assertNotNull(response.get(1));
+        assertNotNull(response.get(2));
+        assertNotEquals(response.get(0), response.get(1));
+        assertNotEquals(response.get(0), response.get(2));
+        assertNotEquals(response.get(1), response.get(2));
+    }
+
+    @Test
+    @DisplayName("addUniqueNumber(): 리스트에 중복된 숫자 존재하지 않을 경우 리스트에 추가")
+    void addUniqueNumber(){
+        // given
+        int num = 3;
+        List<Integer> answers = new ArrayList<>();
+        answers.add(4);
+        answers.add(1);
+
+        // when
+        Baseball baseball = new Baseball();
+        List<Integer> response = baseball.addUniqueNumber(num, answers);
+
+        // then
+        assertEquals(response.size(), 3);
+        assertEquals(response.get(0), answers.get(0));
+        assertEquals(response.get(1), answers.get(1));
+        assertEquals(response.get(2), num);
+    }
+
+    @Test
+    @DisplayName("addUniqueNumber(): 리스트에 중복 숫자 존재하는 경우 리스트에 추가 안됨")
+    void addDuplicatedNumber(){
+        // given
+        int num = 1;
+        List<Integer> answers = new ArrayList<>();
+        answers.add(4);
+        answers.add(1);
+
+        // when
+        Baseball baseball = new Baseball();
+        List<Integer> response = baseball.addUniqueNumber(num, answers);
+
+        // then
+        assertEquals(response.size(), answers.size());
+        assertEquals(response.get(0), answers.get(0));
+        assertEquals(response.get(1), answers.get(1));
+    }
+
+}
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");
-    }
-}