2단계 - 문자열 덧셈 계산기

src/main/java/study/step2/StringAddCalculator.java

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+package study.step2;
+
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+public class StringAddCalculator {
+
+    public static int splitAndSum(String text) {
+        if (text == null || text.isEmpty()) {
+            return 0;
+        }
+
+        String[] tokens;
+
+        if (text.startsWith("//")) {
+            Matcher m = Pattern.compile("//(.)\n(.*)").matcher(text);
+            if (m.find()) {
+                String customDelimiter = m.group(1);
+                tokens = m.group(2).split(Pattern.quote(customDelimiter));
+            } else {
+                throw new RuntimeException("커스텀 구분자 형식이 올바르지 않습니다.");
+            }
+        } else {
+            tokens = text.split(",|:");
+        }
+
+        int sum = 0;
+        for (String token : tokens) {
+            int number;
+            try {
+                number = Integer.parseInt(token);
+            } catch (NumberFormatException e) {
+                throw new RuntimeException("숫자가 아닌 값이 포함되어 있습니다: " + token);
+            }
+            if (number < 0) {
+                throw new RuntimeException("음수는 허용되지 않습니다: " + number);
+            }
+            sum += number;
+        }
+        return sum;
+    }
+}

src/test/java/study/step1/SetTest.java

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+package study.step1;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Nested;
+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;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+public class SetTest {
+
+    private Set<Integer> numbers;
+
+    @BeforeEach
+    void setUp() {
+        numbers = new HashSet<>();
+        numbers.add(1);
+        numbers.add(1);
+        numbers.add(2);
+        numbers.add(3);
+    }
+
+    @Nested
+    class requirements1 {
+        @Test
+        void setSize() {
+            assertEquals(3, numbers.size());
+        }
+    }
+
+    @Nested
+    class requirements2 {
+        @ParameterizedTest
+        @ValueSource(ints = {1, 2, 3})
+        void parameterizedValueScoreTest(int number) {
+            assertThat(numbers.contains(number)).isTrue();
+        }
+    }
+
+    @Nested
+    class requirements3 {
+        @ParameterizedTest
+        @CsvSource({
+                "1, true",
+                "2, true",
+                "3, true",
+                "4, false",
+                "5, false"
+        })
+        void parameterizedCsvSourceTest(int number, boolean expected) {
+            assertThat(numbers.contains(number)).isEqualTo(expected);
+        }
+    }
+}

src/test/java/study/step1/StringTest.java

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+package study.step1;
+
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Nested;
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.AssertionsForClassTypes.assertThat;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+public class StringTest {
+
+    @Nested
+    class requirements1 {
+        @Test
+        void splitString1() {
+            String input = "1,2";
+            String[] result = input.split(",");
+            assertThat(result).containsExactly("1", "2");
+        }
+
+        @Test
+        void splitString2() {
+            String input = "1";
+            String[] result = input.split(",");
+            assertThat(result).containsExactly("1");
+        }
+    }
+
+    @Nested
+    class requirements2 {
+        @Test
+        void substringString() {
+            String input = "(1,2)";
+            String result = input.substring(1, input.length() - 1);
+            assertThat(result).isEqualTo("1,2");
+        }
+    }
+
+    @Nested
+    class requirements3 {
+        @Test
+        @DisplayName("문자열 \"abc\"에서 범위를 벗어난 인덱스의 문자를 요청하면 예외가 발생한다")
+        void charAtString() {
+            String input = "abc";
+            int index = 10;
+            assertThrows(StringIndexOutOfBoundsException.class, () -> {
+                input.charAt(index);
+            }, "인덱스 " + index + " 은 문자열의 길이를 벗어나므로 예외가 발생해야 한다");
+        }
+    }
+
+}

src/test/java/study/step2/StringAddCalculatorTest.java

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+package study.step2;
+
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
+
+public class StringAddCalculatorTest {
+    @Test
+    public void splitAndSum_null_또는_빈문자() {
+        int result = StringAddCalculator.splitAndSum(null);
+        assertThat(result).isEqualTo(0);
+
+        result = StringAddCalculator.splitAndSum("");
+        assertThat(result).isEqualTo(0);
+    }
+
+    @Test
+    public void splitAndSum_숫자하나() throws Exception {
+        int result = StringAddCalculator.splitAndSum("1");
+        assertThat(result).isEqualTo(1);
+    }
+
+    @Test
+    public void splitAndSum_쉼표구분자() throws Exception {
+        int result = StringAddCalculator.splitAndSum("1,2");
+        assertThat(result).isEqualTo(3);
+    }
+
+    @Test
+    public void splitAndSum_쉼표_또는_콜론_구분자() throws Exception {
+        int result = StringAddCalculator.splitAndSum("1,2:3");
+        assertThat(result).isEqualTo(6);
+    }
+
+    @Test
+    public void splitAndSum_custom_구분자() throws Exception {
+        int result = StringAddCalculator.splitAndSum("//;\n1;2;3");
+        assertThat(result).isEqualTo(6);
+    }
+
+    @Test
+    public void splitAndSum_negative() throws Exception {
+        assertThatThrownBy(() -> StringAddCalculator.splitAndSum("-1,2,3"))
+                .isInstanceOf(RuntimeException.class);
+    }
+}