diff --git a/src/main/java/baseboll/StringCalculator.java b/src/main/java/baseboll/StringCalculator.java
new file mode 100644
index 000000000..71d99ec45
--- /dev/null
+++ b/src/main/java/baseboll/StringCalculator.java
@@ -0,0 +1,42 @@
+package baseboll;
+
+public class StringCalculator {
+    public String[] toStringArray(String s){
+        return s.split(" ");
+    }
+
+    public int add(int a, int b){
+        return a + b;
+    }
+
+    public int subtract(int a, int b){
+        return a - b;
+    }
+
+    public int multiply(int a, int b){
+        return a * b;
+    }
+
+    public int divide(int a, int b){
+        if (b == 0) throw new IllegalArgumentException("0으로 나눌 수 없다 인마");
+        return a / b;
+    }
+
+    public int calculate(int a, int b, String operator){
+        if (operator.equals("+")) return add(a, b);
+        if (operator.equals("-")) return subtract(a,b);
+        if (operator.equals("*")) return multiply(a,b);
+        if (operator.equals("/")) return divide(a,b);
+
+        throw new IllegalArgumentException("잘못된 입력이다 인마");
+    }
+
+    public int calculateString(String s){
+        String[] stringArray = toStringArray(s);
+        int answer = Integer.parseInt(stringArray[0]);
+        for (int i = 1; i < stringArray.length; i += 2) {
+            answer = calculate(answer, Integer.parseInt(stringArray[i + 1]), stringArray[i]);
+        }
+        return answer;
+    }
+}
diff --git a/src/main/java/baseboll/myTrial/allInOne/BadCaseGame.java b/src/main/java/baseboll/myTrial/allInOne/BadCaseGame.java
new file mode 100644
index 000000000..7644af71e
--- /dev/null
+++ b/src/main/java/baseboll/myTrial/allInOne/BadCaseGame.java
@@ -0,0 +1,109 @@
+package baseboll.myTrial.allInOne;
+
+
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.util.*;
+
+public class BadCaseGame {
+    private final BufferedReader br;
+    public BadCaseGame(BufferedReader br) {
+        this.br = br;
+    }
+    public void game() throws IOException {
+        String answer = String.valueOf(makeRandomAnswer());
+        progressGame(answer);
+    }
+    private void progressGame(String answer) throws IOException {
+        String input = getInput(); // 사용자에게 입력값 받아오기
+        if (!isPossible(input)) progressGame(answer);
+        if (isCorrect(input, answer)) {
+            continueOrNot();
+            return;
+        }
+        countTotal(input, answer);
+        progressGame(answer);
+    }
+
+    private boolean isPossible(String input) {
+        return false;
+    }
+
+    private void countTotal(String input, String answer){
+        int strikeCount = strikeCountChecker(input, answer);
+        int ballCount = ballCountChecker(input, answer);
+        StringBuilder sb = new StringBuilder();
+        if (strikeCount == 0 & ballCount == 0) {
+            System.out.println("낫싱");
+            return;
+        }
+        if (strikeCount != 0) sb.append(strikeCount).append("스트라이크");
+        if (ballCount != 0) sb.append(ballCount).append("볼");
+        System.out.println(sb.toString());
+    }
+
+    private int makeRandomAnswer() {
+        List<Integer> digits = new ArrayList<>();
+        for (int i = 0; i < 10; i++) {
+            digits.add(i);
+        }
+        Collections.shuffle(digits);
+        int firstDigit = digits.get(0);
+        int secondDigit = digits.get(1);
+        int thirdDigit = digits.get(2);
+        return firstDigit * 100 + secondDigit * 10 + thirdDigit;
+    }
+
+    private String getInput() throws IOException {
+        System.out.println("숫자를 입력 해 주세요");
+        return br.readLine();
+    }
+
+    private void continueOrNot() throws IOException {
+        System.out.println("3개의 숫자를 모두 맞히셨습니다! 게임 종료");
+        System.out.println("게임을 새로 시작하려면 1, 종료하려면 2를 입력하세요.");
+        String input = br.readLine();
+        if (input.equals("1")) {
+            game();
+            return;
+        }
+        if (input.equals("2")) {
+            return;
+        }
+        System.out.println("잘못된 입력입니다.");
+    }
+
+    private int strikeCountChecker(String input, String answer){
+        String[] given = input.split("");
+        String[] ans = answer.split("");
+        int correctCount = 0;
+        for (int i = 0; i < given.length; i++) {
+            correctCount += strikeCheck(given[i], ans[i]);
+        }
+        return correctCount;
+    }
+
+    private int ballCountChecker(String input, String answer){
+        String[] given = input.split("");
+        Set<String> set = new HashSet<>(Arrays.asList(given));
+        int count = 0;
+        for (String s : set) {
+            count += ballCheck(s, answer);
+        }
+        int alreadyCountedStrike = strikeCountChecker(input, answer);
+        if (alreadyCountedStrike != 0) count -= alreadyCountedStrike;
+        return count;
+    }
+
+    private int strikeCheck(String s, String d){
+        return s.equals(d) ? 1 : 0;
+    }
+
+    private int ballCheck(String input, String answer){
+        return answer.contains(input) ? 1 : 0;
+    }
+
+    private boolean isCorrect(String input, String answer){
+        return input.equals(answer);
+    }
+}
diff --git a/src/main/java/baseboll/myTrial/second/Main.java b/src/main/java/baseboll/myTrial/second/Main.java
new file mode 100644
index 000000000..8d9186e83
--- /dev/null
+++ b/src/main/java/baseboll/myTrial/second/Main.java
@@ -0,0 +1,19 @@
+package baseboll.myTrial.second;
+
+import baseboll.myTrial.second.checker.GameChecker;
+import baseboll.myTrial.second.view.GameController;
+import baseboll.myTrial.second.view.InputView;
+import baseboll.myTrial.second.view.OutputView;
+
+import java.io.IOException;
+
+public class Main {
+    public static void main(String[] args) throws IOException {
+        InputView inputView = new InputView();
+        OutputView outputView = new OutputView();
+        GameChecker gameChecker = new GameChecker();
+        NumberProvider numberProvider = new NumberProvider();
+        GameController gameController = new GameController(inputView, outputView, gameChecker, numberProvider);
+        gameController.game();
+    }
+}
diff --git a/src/main/java/baseboll/myTrial/second/NumberProvider.java b/src/main/java/baseboll/myTrial/second/NumberProvider.java
new file mode 100644
index 000000000..ae254abbd
--- /dev/null
+++ b/src/main/java/baseboll/myTrial/second/NumberProvider.java
@@ -0,0 +1,23 @@
+package baseboll.myTrial.second;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+
+public class NumberProvider {
+    private int makeInteger() {
+        List<Integer> digits = new ArrayList<>();
+        for (int i = 0; i < 10; i++) {
+            digits.add(i);
+        }
+        Collections.shuffle(digits);
+        int firstDigit = digits.get(0);
+        int secondDigit = digits.get(1);
+        int thirdDigit = digits.get(2);
+        return firstDigit * 100 + secondDigit * 10 + thirdDigit;
+    }
+
+    public String makeRandomAnswer(){
+        return String.valueOf(this.makeInteger());
+    }
+}
diff --git a/src/main/java/baseboll/myTrial/second/checker/BallChecker.java b/src/main/java/baseboll/myTrial/second/checker/BallChecker.java
new file mode 100644
index 000000000..46bf41988
--- /dev/null
+++ b/src/main/java/baseboll/myTrial/second/checker/BallChecker.java
@@ -0,0 +1,22 @@
+package baseboll.myTrial.second.checker;
+
+import java.util.Arrays;
+import java.util.HashSet;
+import java.util.Set;
+
+public class BallChecker extends Checker {
+    private int checkBall(String s, String answer){
+        return answer.contains(s) ? 1 : 0;
+    }
+
+    public int countBall(String input, String answer, int strikeCount){
+        String[] given = input.split("");
+        Set<String> set = new HashSet<>(Arrays.asList(given));
+        int count = 0;
+        for (String s : set) {
+            count += checkBall(s, answer);
+        }
+        if (strikeCount != 0) count -= strikeCount;
+        return count;
+    }
+}
diff --git a/src/main/java/baseboll/myTrial/second/checker/Checker.java b/src/main/java/baseboll/myTrial/second/checker/Checker.java
new file mode 100644
index 000000000..41bf898fb
--- /dev/null
+++ b/src/main/java/baseboll/myTrial/second/checker/Checker.java
@@ -0,0 +1,7 @@
+package baseboll.myTrial.second.checker;
+
+abstract class Checker {
+
+    public Checker() {
+    }
+}
diff --git a/src/main/java/baseboll/myTrial/second/checker/CorrectChecker.java b/src/main/java/baseboll/myTrial/second/checker/CorrectChecker.java
new file mode 100644
index 000000000..78c497eb6
--- /dev/null
+++ b/src/main/java/baseboll/myTrial/second/checker/CorrectChecker.java
@@ -0,0 +1,8 @@
+package baseboll.myTrial.second.checker;
+
+public class CorrectChecker extends Checker{
+
+    public boolean isCorrect(String input, String answer){
+        return input.equals(answer);
+    }
+}
diff --git a/src/main/java/baseboll/myTrial/second/checker/GameChecker.java b/src/main/java/baseboll/myTrial/second/checker/GameChecker.java
new file mode 100644
index 000000000..3938074ee
--- /dev/null
+++ b/src/main/java/baseboll/myTrial/second/checker/GameChecker.java
@@ -0,0 +1,31 @@
+package baseboll.myTrial.second.checker;
+
+public class GameChecker {
+    private NothingChecker nothingChecker;
+    private CorrectChecker correctChecker;
+    private StrikeChecker strikeChecker;
+    private BallChecker ballChecker;
+
+    public GameChecker() {
+        init();
+    }
+
+    private void init() {
+        this.ballChecker = new BallChecker();
+        this.correctChecker = new CorrectChecker();
+        this.nothingChecker = new NothingChecker();
+        this.strikeChecker = new StrikeChecker();
+    }
+
+    public String check(String input, String answer){
+        if (this.correctChecker.isCorrect(input, answer)) return "정답";
+        int strikeCount = strikeChecker.countStrike(input, answer);
+        int ballCount = ballChecker.countBall(input, answer, strikeCount);
+        if (nothingChecker.isNothing(strikeCount, ballCount)) return "낫싱";
+        String ball = ballCount + "볼";
+        if (strikeCount == 0 && ballCount != 0) return ball;
+        String strike = strikeCount + "스트라이크";
+        if (ballCount == 0 && strikeCount != 0) return strike;
+        return strike + ball;
+    }
+}
\ No newline at end of file
diff --git a/src/main/java/baseboll/myTrial/second/checker/NothingChecker.java b/src/main/java/baseboll/myTrial/second/checker/NothingChecker.java
new file mode 100644
index 000000000..5673c1a03
--- /dev/null
+++ b/src/main/java/baseboll/myTrial/second/checker/NothingChecker.java
@@ -0,0 +1,8 @@
+package baseboll.myTrial.second.checker;
+
+public class NothingChecker extends Checker{
+
+    public boolean isNothing(int strikeCount, int ballCount){
+        return strikeCount == 0 && ballCount == 0;
+    }
+}
diff --git a/src/main/java/baseboll/myTrial/second/checker/StrikeChecker.java b/src/main/java/baseboll/myTrial/second/checker/StrikeChecker.java
new file mode 100644
index 000000000..415c2c0a7
--- /dev/null
+++ b/src/main/java/baseboll/myTrial/second/checker/StrikeChecker.java
@@ -0,0 +1,16 @@
+package baseboll.myTrial.second.checker;
+
+public class StrikeChecker extends Checker{
+    private int checkStrike(String aInput, String aAnswer){
+        return aInput.equals(aAnswer) ? 1 : 0;
+    }
+    public int countStrike(String input, String answer){
+        String[] inputs = input.split("");
+        String[] answers = answer.split("");
+        int strikeCount = 0;
+        for (int i = 0; i < inputs.length; i++) {
+            strikeCount += checkStrike(inputs[i], answers[i]);
+        }
+        return strikeCount;
+    }
+}
diff --git a/src/main/java/baseboll/myTrial/second/view/GameController.java b/src/main/java/baseboll/myTrial/second/view/GameController.java
new file mode 100644
index 000000000..f824df95d
--- /dev/null
+++ b/src/main/java/baseboll/myTrial/second/view/GameController.java
@@ -0,0 +1,37 @@
+package baseboll.myTrial.second.view;
+
+import baseboll.myTrial.second.NumberProvider;
+import baseboll.myTrial.second.checker.GameChecker;
+
+import java.io.IOException;
+
+public class GameController {
+    private final InputView inputView;
+    private final OutputView outputView;
+    private final GameChecker gameChecker;
+    private final NumberProvider numberProvider;
+
+
+    public GameController(InputView inputView, OutputView outputView, GameChecker gameChecker, NumberProvider numberProvider) {
+        this.inputView = inputView;
+        this.outputView = outputView;
+        this.gameChecker = gameChecker;
+        this.numberProvider = numberProvider;
+    }
+
+    private boolean correct(String input, String answer) {
+        return input.equals(answer);
+    }
+
+    public void game() throws IOException {
+        String answer = numberProvider.makeRandomAnswer();
+        System.out.println(answer);
+        String input = "";
+        while (!correct(input, answer)){
+            input = inputView.getInput(); // 인펏부터 받는다
+            String checked = gameChecker.check(input, answer);
+            outputView.sendOutput(checked);
+        }
+        if (inputView.wantContinue()) game();
+    }
+}
diff --git a/src/main/java/baseboll/myTrial/second/view/InputView.java b/src/main/java/baseboll/myTrial/second/view/InputView.java
new file mode 100644
index 000000000..79455c2cc
--- /dev/null
+++ b/src/main/java/baseboll/myTrial/second/view/InputView.java
@@ -0,0 +1,41 @@
+package baseboll.myTrial.second.view;
+
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+
+public class InputView {
+    private final BufferedReader br;
+
+    public InputView() {
+        this.br = new BufferedReader(new InputStreamReader(System.in));
+    }
+
+    public String getInput() throws IOException {
+        System.out.println("숫자를 입력 해 주세요");
+        String input = br.readLine();
+        if (!isProperInput(input)) {
+            getInput();
+        }
+        return input;
+    }
+
+    public boolean wantContinue() throws IOException {
+        String input = br.readLine();
+        return input.equals("1");
+    }
+
+    public boolean isProperInput(String s) {
+        if (s.length() != 3) {
+            System.out.println("3자리 숫자를 입력해주세요");
+            return false;
+        }
+        try {
+            Integer.parseInt(s);
+        } catch (NumberFormatException e) {
+            System.out.println("숫자만 입력해주세요");
+            return false;
+        }
+        return true;
+    }
+}
diff --git a/src/main/java/baseboll/myTrial/second/view/OutputView.java b/src/main/java/baseboll/myTrial/second/view/OutputView.java
new file mode 100644
index 000000000..2ef1d88a9
--- /dev/null
+++ b/src/main/java/baseboll/myTrial/second/view/OutputView.java
@@ -0,0 +1,22 @@
+package baseboll.myTrial.second.view;
+
+public class OutputView {
+    public void nothing(){
+        System.out.println("낫싱");
+    }
+    public void gameEnd(){
+        System.out.println("3개의 숫자를 모두 맞히셨습니다! 게임 종료" + "\n" + "게임을 새로 시작하려면 1, 종료하려면 2를 입력하세요.");
+    }
+    public void sendOutput(String checkResult){
+        if (checkResult.equals("정답")) {
+            gameEnd();
+            return;
+        }
+        if (checkResult.equals("낫싱")) {
+            nothing();
+            return;
+        }
+        if (checkResult.equals("")) return;
+        System.out.println(checkResult);
+    }
+}
diff --git a/src/main/java/tdd/Ball.java b/src/main/java/tdd/Ball.java
new file mode 100644
index 000000000..7fc0e8014
--- /dev/null
+++ b/src/main/java/tdd/Ball.java
@@ -0,0 +1,40 @@
+package tdd;
+
+import java.util.Objects;
+
+public class Ball {
+    private final int location;
+    private final int value;
+
+    public Ball(int location, int value) {
+        this.location = location;
+        this.value = value;
+    }
+
+    public BallStatus play(Ball userBall) {
+        if (this.equals(userBall)) {
+            return BallStatus.STRIKE;
+        }
+        if (isBall(userBall)) {
+            return BallStatus.BALL;
+        }
+        return BallStatus.NOTHING;
+    }
+
+    private boolean isBall(Ball userBall) {
+        return this.value == userBall.value;
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) return true;
+        if (o == null || getClass() != o.getClass()) return false;
+        Ball ball = (Ball) o;
+        return location == ball.location && value == ball.value;
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(location, value);
+    }
+}
diff --git a/src/main/java/tdd/BallStatus.java b/src/main/java/tdd/BallStatus.java
new file mode 100644
index 000000000..12c2c013c
--- /dev/null
+++ b/src/main/java/tdd/BallStatus.java
@@ -0,0 +1,13 @@
+package tdd;
+
+public enum BallStatus {
+    BALL, STRIKE, NOTHING;
+
+    public boolean isBall(){
+        return this == BALL;
+    }
+
+    public boolean isStrike() {
+        return this == STRIKE;
+    }
+}
diff --git a/src/main/java/tdd/Balls.java b/src/main/java/tdd/Balls.java
new file mode 100644
index 000000000..a7bac768f
--- /dev/null
+++ b/src/main/java/tdd/Balls.java
@@ -0,0 +1,43 @@
+package tdd;
+
+import java.util.List;
+import java.util.stream.Collectors;
+import java.util.stream.IntStream;
+
+public class Balls {
+    List<Ball> balls;
+
+    public Balls(List<Integer> balls) {
+        isValid(balls);
+        this.balls = mapBalls(balls);
+    }
+
+    private static List<Ball> mapBalls(List<Integer> balls) {
+        return IntStream.range(0, balls.size())
+                .mapToObj(i -> new Ball(i + 1, balls.get(i)))
+                .collect(Collectors.toList());
+    }
+
+    private void isValid(List<Integer> balls) {
+        if (balls.size() != 3) {
+            throw new IllegalArgumentException("잘못 입력");
+        }
+    }
+
+    public BallStatus play(Ball ball) {
+        return this.balls.stream()
+                .map(answer -> answer.play(ball))
+                .filter(ballStatus -> ballStatus != BallStatus.NOTHING)
+                .findFirst()
+                .orElse(BallStatus.NOTHING);
+    }
+
+    public PlayerResult play(List<Integer> userInput){
+        List<Ball> mappedBalls = mapBalls(userInput);
+        PlayerResult result = new PlayerResult();
+        for (Ball mappedBall : mappedBalls) {
+            result.report(play(mappedBall));
+        }
+        return result;
+    }
+}
diff --git a/src/main/java/tdd/PlayerResult.java b/src/main/java/tdd/PlayerResult.java
new file mode 100644
index 000000000..aa0026968
--- /dev/null
+++ b/src/main/java/tdd/PlayerResult.java
@@ -0,0 +1,19 @@
+package tdd;
+
+public class PlayerResult {
+    private int strikeCount = 0;
+    private int ballCount = 0;
+
+    public int getBall() {
+        return ballCount;
+    }
+
+    public int getStrike(){
+        return strikeCount;
+    }
+
+    public void report(BallStatus result) {
+        if (result.isBall()) ballCount += 1;
+        if (result.isStrike()) strikeCount += 1;
+    }
+}
diff --git a/src/test/java/StringCalculatorTest.java b/src/test/java/StringCalculatorTest.java
new file mode 100644
index 000000000..1df4b32a8
--- /dev/null
+++ b/src/test/java/StringCalculatorTest.java
@@ -0,0 +1,81 @@
+import baseboll.StringCalculator;
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.CsvSource;
+import org.junit.jupiter.params.provider.ValueSource;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
+
+class StringCalculatorTest {
+    static StringCalculator sc;
+    @BeforeAll
+    static void init(){
+        sc = new StringCalculator();
+    }
+
+    @ParameterizedTest
+    @ValueSource(strings = {"1 * 3 / 2", "1 * 2 * 3 * 4"})
+    void toStringArray(String s) {
+        String[] stringArray = sc.toStringArray(s);
+
+        assertThat(stringArray).contains("*");
+    }
+
+    @ParameterizedTest
+    @CsvSource(value = {"1:3", "2:2", "3:1"}, delimiter = ':')
+    void add(int a, int b) {
+        int added = sc.add(a, b);
+
+        assertThat(added).isEqualTo(4);
+    }
+
+    @ParameterizedTest
+    @CsvSource(value = {"15:13", "4:2", "3:1"}, delimiter = ':')
+    void subtract(int a, int b) {
+        int subtracted = sc.subtract(a, b);
+
+        assertThat(subtracted).isEqualTo(2);
+    }
+
+    @ParameterizedTest
+    @CsvSource(value = {"1:8", "4:2", "2:4"}, delimiter = ':')
+    void multiply(int a, int b) {
+        int multiplied = sc.multiply(a, b);
+
+        assertThat(multiplied).isEqualTo(8);
+    }
+
+    @ParameterizedTest
+    @CsvSource(value = {"4:2", "8:4", "16:8"}, delimiter = ':')
+    void divideSuccess(int a, int b) {
+        int divided = sc.divide(a, b);
+        assertThat(divided).isEqualTo(2);
+    }
+
+    @ParameterizedTest
+    @CsvSource(value = {"10:0", "3:0"}, delimiter = ':')
+    void divideFailByDivideBy0(int a, int b){
+        assertThatThrownBy(() -> sc.divide(a, b));
+    }
+
+    @ParameterizedTest
+    @CsvSource(value = {"3:5:*", "15:0:-", "30:2:/", "8:7:+"}, delimiter = ':')
+    void calculateSuccess(int a, int b, String operator) {
+        int calculate = sc.calculate(a, b, operator);
+        assertThat(calculate).isEqualTo(15);
+    }
+
+    @ParameterizedTest
+    @CsvSource(value = {"3:5:음", "15:0:오", "30:2:아", "8:7:예", "1:1:?"}, delimiter = ':')
+    void calculateFailByOperator(int a, int b, String operator){
+        assertThatThrownBy(() -> sc.calculate(a, b, operator));
+    }
+
+    @ParameterizedTest
+    @ValueSource(strings = {"1 * 3 * 5", "5 * 3 * 1", "10 + 10 - 5"})
+    void calculateString(String s) {
+        int calculated = sc.calculateString(s);
+        assertThat(calculated).isEqualTo(15);
+    }
+}
\ No newline at end of file
diff --git a/src/test/java/baseboll/checker/CheckerTest.java b/src/test/java/baseboll/checker/CheckerTest.java
new file mode 100644
index 000000000..7bd9032f5
--- /dev/null
+++ b/src/test/java/baseboll/checker/CheckerTest.java
@@ -0,0 +1,79 @@
+package baseboll.checker;
+
+
+import baseboll.myTrial.second.checker.*;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class CheckerTest {
+    @Test
+    void nothingCheckerTest(){
+        NothingChecker nothingChecker = new NothingChecker();
+        boolean nothing = nothingChecker.isNothing(0, 0);
+        assertTrue(nothing);
+        nothing = nothingChecker.isNothing(1,2);
+        assertFalse(nothing);
+    }
+
+    @Test
+    void correctCheckerTest(){
+        CorrectChecker correctChecker = new CorrectChecker();
+        String input = "123";
+        String answer = "123";
+        boolean correct = correctChecker.isCorrect(input, answer);
+        assertTrue(correct);
+        correct = correctChecker.isCorrect(input, "125");
+        assertFalse(correct);
+    }
+
+    @Test
+    void strikerCheckerTest(){
+        StrikeChecker strikeChecker = new StrikeChecker();
+        int strike = strikeChecker.countStrike("123", "128");
+        assertEquals(2, strike);
+    }
+
+    @Test
+    void ballCheckerTest(){
+        BallChecker ballChecker = new BallChecker();
+        int ball = ballChecker.countBall("123", "312", 0);
+        assertEquals(3, ball);
+    }
+
+    @Test
+    void gameCheckerCorrectTest(){
+        GameChecker gameChecker = new GameChecker();
+        String input = "123";
+        String answer = "123";
+        String checked = gameChecker.check(input, answer);
+        assertEquals("정답", checked);
+    }
+
+    @Test
+    void gameCheckerStrikeTest(){
+        GameChecker gameChecker = new GameChecker();
+        String input = "126";
+        String answer = "123";
+        String checked = gameChecker.check(input, answer);
+        assertEquals("2스트라이크", checked);
+    }
+
+    @Test
+    void gameCheckerStrikeAndBallTest(){
+        GameChecker gameChecker = new GameChecker();
+        String input = "132";
+        String answer = "123";
+        String checked = gameChecker.check(input, answer);
+        assertEquals("1스트라이크2볼", checked);
+    }
+
+    @Test
+    void gameCheckerNothingTest(){
+        GameChecker gameChecker = new GameChecker();
+        String input = "789";
+        String answer = "123";
+        String checked = gameChecker.check(input, answer);
+        assertEquals("낫싱", checked);
+    }
+}
\ No newline at end of file
diff --git a/src/test/java/study/SetTest.java b/src/test/java/study/SetTest.java
new file mode 100644
index 000000000..c57db4539
--- /dev/null
+++ b/src/test/java/study/SetTest.java
@@ -0,0 +1,51 @@
+package study;
+
+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.Assertions.assertThat;
+
+public class SetTest {
+    private Set<Integer> numbers;
+
+    private Set<Integer> anotherNumbers;
+    @BeforeEach
+    void setUp() {
+        numbers = new HashSet<>();
+        numbers.add(1);
+        numbers.add(1);
+        numbers.add(2);
+        numbers.add(3);
+
+        anotherNumbers = new HashSet<>();
+        anotherNumbers.add(4);
+        anotherNumbers.add(5);
+    }
+
+    // Test Case 구현
+    @Test
+    @DisplayName("Set.size() 매서드가 셋의 크기를 반환함을 테스트")
+    void size(){
+        int size = numbers.size();
+        assertThat(size).isEqualTo(3);
+    }
+
+    @ParameterizedTest
+    @ValueSource(ints = {1, 2, 3})
+    void simpleContains(int setNumbers){
+        assertThat(numbers).contains(setNumbers);
+    }
+
+    @ParameterizedTest
+    @CsvSource(value = {"1:true", "2:true", "3:true", "4:false", "5:false"}, delimiter = ':')
+    void contains(int pass, boolean notPass){
+        assertThat(numbers.contains(pass)).isEqualTo(notPass);
+    }
+}
\ No newline at end of file
diff --git a/src/test/java/study/StringTest.java b/src/test/java/study/StringTest.java
index 43e47d90b..9b5eb3621 100644
--- a/src/test/java/study/StringTest.java
+++ b/src/test/java/study/StringTest.java
@@ -1,8 +1,10 @@
 package study;
 
+import org.junit.jupiter.api.DisplayName;
 import org.junit.jupiter.api.Test;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
 
 public class StringTest {
     @Test
@@ -10,4 +12,31 @@ void replace() {
         String actual = "abc".replace("b", "d");
         assertThat(actual).isEqualTo("adc");
     }
+
+    @Test
+    void split(){
+        String actual = "1,2";
+        String[] split = actual.split(",");
+        assertThat(split).contains("1").contains("2"); // 1
+        assertThat(split).containsExactly("1", "2"); // 2
+    }
+
+    @Test
+    void substring(){
+        String actual = "(1,2)";
+        String substring = actual.substring(1, actual.length() - 1);
+        assertThat(substring).isEqualTo("1,2");
+    }
+
+    @Test
+    @DisplayName("String.charAt 매서드에서 유효하지 않은 인덱스를 인자로 준 경우")
+    void charAt(){
+        String actual = "abc";
+        int idx = 3;
+        assertThatThrownBy(() -> {
+            actual.charAt(idx);
+        })
+                .isInstanceOf(StringIndexOutOfBoundsException.class)
+                .hasMessageContaining("String index out of range: " + idx);;
+    }
 }
diff --git a/src/test/java/tdd/BallTest.java b/src/test/java/tdd/BallTest.java
new file mode 100644
index 000000000..3132fd186
--- /dev/null
+++ b/src/test/java/tdd/BallTest.java
@@ -0,0 +1,31 @@
+package tdd;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class BallTest {
+    static Ball comBall;
+    @BeforeEach
+    void comBall(){
+        comBall = new Ball(1,1);
+    }
+    @Test
+    void nothing(){
+        Ball userBall = new Ball(1,9);
+        assertThat(comBall.play(userBall)).isEqualTo(BallStatus.NOTHING);
+    }
+
+    @Test
+    void ball(){
+        Ball userBall = new Ball(2,1);
+        assertThat(comBall.play(userBall)).isEqualTo(BallStatus.BALL);
+    }
+
+    @Test
+    void strike(){
+        Ball userBall = new Ball(1,1);
+        assertThat(comBall.play(userBall)).isEqualTo(BallStatus.STRIKE);
+    }
+}
diff --git a/src/test/java/tdd/BallsTest.java b/src/test/java/tdd/BallsTest.java
new file mode 100644
index 000000000..1c2ad7426
--- /dev/null
+++ b/src/test/java/tdd/BallsTest.java
@@ -0,0 +1,47 @@
+package tdd;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import java.util.Arrays;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class BallsTest {
+    static Balls balls;
+    @BeforeEach
+    void setBall(){
+        balls = new Balls(Arrays.asList(1, 2, 3));
+    }
+
+    @Test
+    void play_1Ball1Strike(){
+        PlayerResult result = balls.play(Arrays.asList(1,3,6));
+        assertThat(result.getBall()).isEqualTo(1);
+        assertThat(result.getStrike()).isEqualTo(1);
+    }
+    @Test
+    void play_Nothing(){
+        PlayerResult result = balls.play(Arrays.asList(4,5,6));
+        assertThat(result.getBall()).isEqualTo(0);
+        assertThat(result.getStrike()).isEqualTo(0);
+    }
+    @Test
+    void nothing(){
+        Ball ball = new Ball(1, 9);
+        BallStatus status = balls.play(ball);
+        assertThat(status).isEqualTo(BallStatus.NOTHING);
+    }
+
+    @Test
+    void ball(){
+        Ball ball = new Ball(1, 3);
+        assertThat(balls.play(ball)).isEqualTo(BallStatus.BALL);
+    }
+
+    @Test
+    void strike(){
+        Ball ball = new Ball(1, 1);
+        assertThat(balls.play(ball)).isEqualTo(BallStatus.STRIKE);
+    }
+}