JUnit 5 기초: 단위 테스트

import org.junit.jupiter.api.*;
import static org.junit.jupiter.api.Assertions.*;

class CalculatorTest {

    private Calculator calculator;

    @BeforeEach
    void setUp() {
        calculator = new Calculator();
    }

    @Test
    @DisplayName("덧셈 정상 동작")
    void add_positive_numbers() {
        assertEquals(5, calculator.add(2, 3));
    }

    @Test
    void divide_by_zero_throws() {
        ArithmeticException ex = assertThrows(
            ArithmeticException.class,
            () -> calculator.divide(10, 0)
        );
        assertTrue(ex.getMessage().contains("zero"));
    }

    @AfterEach
    void tearDown() { /* cleanup */ }
}

@ParameterizedTest
@ValueSource(ints = {1, 3, 5, 7, 9})
void odd_numbers(int n) {
    assertTrue(n % 2 == 1);
}


@ParameterizedTest
@CsvSource({
    "1, 1, 2",
    "2, 3, 5",
    "10, 20, 30",
})
void add_table(int a, int b, int expected) {
    assertEquals(expected, calculator.add(a, b));
}


@ParameterizedTest
@MethodSource("provideTestCases")
void from_method(String input, int expected) {
    assertEquals(expected, parseInt(input));
}

static Stream<Arguments> provideTestCases() {
    return Stream.of(
        Arguments.of("1", 1),
        Arguments.of("100", 100),
        Arguments.of("0", 0)
    );
}

class UserServiceTest {

    @Test
    @DisplayName("이메일 중복 시 예외")
    void signup_duplicate_email_throws() {
        // given
        UserRepository mockRepo = mock(UserRepository.class);
        when(mockRepo.existsByEmail("alice@example.com")).thenReturn(true);

        UserService service = new UserService(mockRepo, mock(PasswordEncoder.class));

        // when & then
        assertThrows(DuplicateEmailException.class, () ->
            service.signup(new SignupDto("alice@example.com", "pass", "Alice")));
    }
}

import static org.assertj.core.api.Assertions.*;

@Test
void assertj_examples() {
    List<String> names = List.of("Alice", "Bob", "Charlie");

    assertThat(names)
        .hasSize(3)
        .contains("Alice")
        .doesNotContain("Dave");

    assertThat(names.get(0))
        .startsWith("A")
        .endsWith("e")
        .hasSize(5);


    User user = new User("Alice", 30);
    assertThat(user)
        .extracting("name", "age")
        .containsExactly("Alice", 30);
}