JUnit5

1. JUnit 5 概述

1.1 架构

1.2 Maven 依赖

<dependency>
    <groupId>org.junit.jupiter</groupId>
    <artifactId>junit-jupiter</artifactId>
    <version>5.10.2</version>
    <scope>test</scope>
</dependency>

2. 常用注解

3. 断言

3.1 标准断言

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

@Test
void testAssertions() {
    assertEquals(4, 2 + 2);
    assertNotEquals(5, 2 + 2);
    assertTrue(4 > 3);
    assertFalse(4 < 3);
    assertNull(null);
    assertNotNull(new Object());
    assertThrows(ArithmeticException.class, () -> {
        int result = 1 / 0;
    });
}

3.2 分组断言

@Test
void testGroupedAssertions() {
    assertAll("person",
        () -> assertEquals("Alice", person.getName()),
        () -> assertEquals(25, person.getAge()),
        () -> assertEquals("alice@example.com", person.getEmail())
    );
}

3.3 超时断言

@Test
void testTimeout() {
    assertTimeout(Duration.ofMillis(500), () -> {
        Thread.sleep(200);
    });
}

4. 生命周期

class LifecycleTest {

    @BeforeAll
    static void setupAll() {
        System.out.println("Before all tests");
    }

    @BeforeEach
    void setup() {
        System.out.println("Before each test");
    }

    @Test
    void test1() {
        System.out.println("Test 1");
    }

    @Test
    void test2() {
        System.out.println("Test 2");
    }

    @AfterEach
    void teardown() {
        System.out.println("After each test");
    }

    @AfterAll
    static void teardownAll() {
        System.out.println("After all tests");
    }
}

5. 参数化测试

5.1 基本参数化

@ParameterizedTest
@ValueSource(ints = {1, 2, 3, 4, 5})
void testPositive(int number) {
    assertTrue(number > 0);
}

@ParameterizedTest
@ValueSource(strings = {"hello", "world", "junit"})
void testNonEmpty(String str) {
    assertFalse(str.isEmpty());
}

5.2 参数来源

5.3 CSV 参数化

@ParameterizedTest
@CsvSource({
    "1, 1, 2",
    "2, 3, 5",
    "-1, 1, 0",
    "0, 0, 0"
})
void testAdd(int a, int b, int expected) {
    assertEquals(expected, Calculator.add(a, b));
}

5.4 MethodSource

@ParameterizedTest
@MethodSource("provideTestData")
void testWithMethodSource(String input, int expected) {
    assertEquals(expected, input.length());
}

static Stream<Arguments> provideTestData() {
    return Stream.of(
        Arguments.of("hello", 5),
        Arguments.of("world", 5),
        Arguments.of("", 0)
    );
}

6. 嵌套测试

@DisplayName("Stack tests")
class StackTest {

    Stack<String> stack;

    @BeforeEach
    void createStack() {
        stack = new Stack<>();
    }

    @Nested
    @DisplayName("when new")
    class WhenNew {

        @Test
        @DisplayName("is empty")
        void isEmpty() {
            assertTrue(stack.isEmpty());
        }

        @Nested
        @DisplayName("after pushing")
        class AfterPushing {

            @BeforeEach
            void pushElement() {
                stack.push("element");
            }

            @Test
            @DisplayName("is not empty")
            void isNotEmpty() {
                assertFalse(stack.isEmpty());
            }
        }
    }
}

7. 扩展模型

7.1 自定义扩展

public class LoggingExtension implements BeforeEachCallback, AfterEachCallback {
    @Override
    public void beforeEach(ExtensionContext context) {
        System.out.println("Before: " + context.getDisplayName());
    }

    @Override
    public void afterEach(ExtensionContext context) {
        System.out.println("After: " + context.getDisplayName());
    }
}

@ExtendWith(LoggingExtension.class)
class MyTest {
    @Test
    void test() { }
}

7.2 常用扩展

8. 最佳实践