JUnit5 应用指南

version: junit5

1. 安装
2. JUnit 注解
3. 编写单元测试
4. 引用和引申

1. 安装

在 pom 中添加依赖

<properties>
  <junit.jupiter.version>5.3.2</junit.jupiter.version>
</properties>

<dependencies>
  <dependency>
    <groupId>org.junit.jupiter</groupId>
    <artifactId>junit-jupiter-api</artifactId>
    <version>${junit.jupiter.version}</version>
    <scope>test</scope>
  </dependency>
  <dependency>
    <groupId>org.junit.jupiter</groupId>
    <artifactId>junit-jupiter-params</artifactId>
    <version>${junit.jupiter.version}</version>
    <scope>test</scope>
  </dependency>
  <dependency>
    <groupId>org.junit.jupiter</groupId>
    <artifactId>junit-jupiter-engine</artifactId>
    <version>${junit.jupiter.version}</version>
    <scope>test</scope>
  </dependency>
</dependencies>

组件间依赖关系：

2. JUnit 注解

Annotation	Description
`@Test`	Denotes that a method is a test method. Unlike JUnit 4’s `@Test` annotation, this annotation does not declare any attributes, since test extensions in JUnit Jupiter operate based on their own dedicated annotations. Such methods are inherited unless they are overridden.
`@ParameterizedTest`	Denotes that a method is a parameterized test. Such methods are inherited unless they are overridden.
`@RepeatedTest`	Denotes that a method is a test template for a repeated test. Such methods are inherited unless they are overridden.
`@TestFactory`	Denotes that a method is a test factory for dynamic tests. Such methods are inherited unless they are overridden.
`@TestInstance`	Used to configure the test instance lifecycle for the annotated test class. Such annotations are inherited.
`@TestTemplate`	Denotes that a method is a template for test cases designed to be invoked multiple times depending on the number of invocation contexts returned by the registered providers. Such methods are inherited unless they are overridden.
`@DisplayName`	Declares a custom display name for the test class or test method. Such annotations are not inherited.
`@BeforeEach`	Denotes that the annotated method should be executed before each `@Test`, `@RepeatedTest`, `@ParameterizedTest`, or `@TestFactory` method in the current class; analogous to JUnit 4’s `@Before`. Such methods are inherited unless they are overridden.
`@AfterEach`	Denotes that the annotated method should be executed after each `@Test`, `@RepeatedTest`, `@ParameterizedTest`, or `@TestFactory` method in the current class; analogous to JUnit 4’s `@After`. Such methods are inherited unless they are overridden.
`@BeforeAll`	Denotes that the annotated method should be executed before all `@Test`, `@RepeatedTest`, `@ParameterizedTest`, and `@TestFactory` methods in the current class; analogous to JUnit 4’s `@BeforeClass`. Such methods are inherited (unless they are hidden or overridden) and must be `static` (unless the "per-class" test instance lifecycle is used).
`@AfterAll`	Denotes that the annotated method should be executed after all `@Test`, `@RepeatedTest`, `@ParameterizedTest`, and `@TestFactory` methods in the current class; analogous to JUnit 4’s `@AfterClass`. Such methods are inherited (unless they are hidden or overridden) and must be `static` (unless the "per-class" test instance lifecycle is used).
`@Nested`	Denotes that the annotated class is a nested, non-static test class. `@BeforeAll` and `@AfterAll`methods cannot be used directly in a `@Nested` test class unless the "per-class" test instance lifecycle is used. Such annotations are not inherited.
`@Tag`	Used to declare tags for filtering tests, either at the class or method level; analogous to test groups in TestNG or Categories in JUnit 4. Such annotations are inherited at the class level but not at the method level.
`@Disabled`	Used to disable a test class or test method; analogous to JUnit 4’s `@Ignore`. Such annotations are not inherited.
`@ExtendWith`	Used to register custom extensions. Such annotations are inherited.

3. 编写单元测试

3.1. 基本的单元测试类和方法

import org.junit.jupiter.api.*;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

class Junit5StandardTests {

    private static final Logger LOGGER = LoggerFactory.getLogger(Junit5StandardTests.class);

    @BeforeAll
    static void beforeAll() {
        LOGGER.info("call beforeAll()");
    }

    @BeforeEach
    void beforeEach() {
        LOGGER.info("call beforeEach()");
    }

    @Test
    void succeedingTest() {
        LOGGER.info("call succeedingTest()");
    }

    @Test
    void failingTest() {
        LOGGER.info("call failingTest()");
        // fail("a failing test");
    }

    @Test
    @Disabled("for demonstration purposes")
    void skippedTest() {
        LOGGER.info("call skippedTest()");
        // not executed
    }

    @AfterEach
    void afterEach() {
        LOGGER.info("call afterEach()");
    }

    @AfterAll
    static void afterAll() {
        LOGGER.info("call afterAll()");
    }
}

3.2. 定制测试类和方法的显示名称

支持普通字符、特殊符号、emoji

import org.junit.jupiter.api.DisplayName;
import org.junit.jupiter.api.Test;

@DisplayName("A special test case")
class JunitDisplayNameDemo {

    @Test
    @DisplayName("Custom test name containing spaces")
    void testWithDisplayNameContainingSpaces() { }

    @Test
    @DisplayName("╯°□°）╯")
    void testWithDisplayNameContainingSpecialCharacters() { }

    @Test
    @DisplayName("😱")
    void testWithDisplayNameContainingEmoji() { }
}

3.3. 断言（Assertions）

import org.junit.jupiter.api.BeforeAll;
import org.junit.jupiter.api.Test;

import static java.time.Duration.ofMillis;
import static java.time.Duration.ofMinutes;
import static org.junit.jupiter.api.Assertions.*;

class AssertionsDemo {

    private static Person person;

    @BeforeAll
    public static void beforeAll() {
        person = new Person("John", "Doe");
    }

    @Test
    void standardAssertions() {
        assertEquals(2, 2);
        assertEquals(4, 4, "The optional assertion message is now the last parameter.");
        assertTrue('a' < 'b', () -> "Assertion messages can be lazily evaluated -- "
            + "to avoid constructing complex messages unnecessarily.");
    }

    @Test
    void groupedAssertions() {
        // In a grouped assertion all assertions are executed, and any
        // failures will be reported together.
        assertAll("person", () -> assertEquals("John", person.getFirstName()),
            () -> assertEquals("Doe", person.getLastName()));
    }

    @Test
    void dependentAssertions() {
        // Within a code block, if an assertion fails the
        // subsequent code in the same block will be skipped.
        assertAll("properties", () -> {
            String firstName = person.getFirstName();
            assertNotNull(firstName);

            // Executed only if the previous assertion is valid.
            assertAll("first name", () -> assertTrue(firstName.startsWith("J")),
                () -> assertTrue(firstName.endsWith("n")));
        }, () -> {
            // Grouped assertion, so processed independently
            // of results of first name assertions.
            String lastName = person.getLastName();
            assertNotNull(lastName);

            // Executed only if the previous assertion is valid.
            assertAll("last name", () -> assertTrue(lastName.startsWith("D")),
                () -> assertTrue(lastName.endsWith("e")));
        });
    }

    @Test
    void exceptionTesting() {
        Throwable exception = assertThrows(IllegalArgumentException.class, () -> {
            throw new IllegalArgumentException("a message");
        });
        assertEquals("a message", exception.getMessage());
    }

    @Test
    void timeoutNotExceeded() {
        // The following assertion succeeds.
        assertTimeout(ofMinutes(2), () -> {
            // Perform task that takes less than 2 minutes.
        });
    }

    @Test
    void timeoutNotExceededWithResult() {
        // The following assertion succeeds, and returns the supplied object.
        String actualResult = assertTimeout(ofMinutes(2), () -> {
            return "a result";
        });
        assertEquals("a result", actualResult);
    }

    @Test
    void timeoutNotExceededWithMethod() {
        // The following assertion invokes a method reference and returns an object.
        String actualGreeting = assertTimeout(ofMinutes(2), AssertionsDemo::greeting);
        assertEquals("Hello, World!", actualGreeting);
    }

    @Test
    void timeoutExceeded() {
        // The following assertion fails with an error message similar to:
        // execution exceeded timeout of 10 ms by 91 ms
        assertTimeout(ofMillis(10), () -> {
            // Simulate task that takes more than 10 ms.
            Thread.sleep(100);
        });
    }

    @Test
    void timeoutExceededWithPreemptiveTermination() {
        // The following assertion fails with an error message similar to:
        // execution timed out after 10 ms
        assertTimeoutPreemptively(ofMillis(10), () -> {
            // Simulate task that takes more than 10 ms.
            Thread.sleep(100);
        });
    }

    private static String greeting() {
        return "Hello, World!";
    }

}

3.4. 假想（Assumptions）

import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assumptions.assumeTrue;
import static org.junit.jupiter.api.Assumptions.assumingThat;

import org.junit.jupiter.api.Test;

class AssumptionsDemo {

    @Test
    void testOnlyOnCiServer() {
        assumeTrue("CI".equals(System.getenv("ENV")));
        // remainder of test
    }

    @Test
    void testOnlyOnDeveloperWorkstation() {
        assumeTrue("DEV".equals(System.getenv("ENV")),
            () -> "Aborting test: not on developer workstation");
        // remainder of test
    }

    @Test
    void testInAllEnvironments() {
        assumingThat("CI".equals(System.getenv("ENV")),
            () -> {
                // perform these assertions only on the CI server
                assertEquals(2, 2);
            });

        // perform these assertions in all environments
        assertEquals("a string", "a string");
    }

}

3.5. 禁用

禁用单元测试类示例：

import org.junit.jupiter.api.Disabled;
import org.junit.jupiter.api.Test;

@Disabled
class DisabledClassDemo {
    @Test
    void testWillBeSkipped() {
    }
}

禁用单元测试方法示例：

import org.junit.jupiter.api.Disabled;
import org.junit.jupiter.api.Test;

class DisabledTestsDemo {

    @Disabled
    @Test
    void testWillBeSkipped() {
    }

    @Test
    void testWillBeExecuted() {
    }
}

3.6. 测试条件

操作系统条件

@Test
@EnabledOnOs(MAC)
void onlyOnMacOs() {
    // ...
}

@TestOnMac
void testOnMac() {
    // ...
}

@Test
@EnabledOnOs({ LINUX, MAC })
void onLinuxOrMac() {
    // ...
}

@Test
@DisabledOnOs(WINDOWS)
void notOnWindows() {
    // ...
}

@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
@Test
@EnabledOnOs(MAC)
@interface TestOnMac {
}

Java 运行时版本条件

@Test
@EnabledOnJre(JAVA_8)
void onlyOnJava8() {
    // ...
}

@Test
@EnabledOnJre({ JAVA_9, JAVA_10 })
void onJava9Or10() {
    // ...
}

@Test
@DisabledOnJre(JAVA_9)
void notOnJava9() {
    // ...
}

系统属性条件

@Test
@EnabledIfSystemProperty(named = "os.arch", matches = ".*64.*")
void onlyOn64BitArchitectures() {
    // ...
}

@Test
@DisabledIfSystemProperty(named = "ci-server", matches = "true")
void notOnCiServer() {
    // ...
}

3.7. 嵌套测试

import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assertions.assertFalse;
import static org.junit.jupiter.api.Assertions.assertThrows;
import static org.junit.jupiter.api.Assertions.assertTrue;

import java.util.EmptyStackException;
import java.util.Stack;

import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.DisplayName;
import org.junit.jupiter.api.Nested;
import org.junit.jupiter.api.Test;

@DisplayName("A stack")
class TestingAStackDemo {

    Stack<Object> stack;

    @Test
    @DisplayName("is instantiated with new Stack()")
    void isInstantiatedWithNew() {
        new Stack<>();
    }

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

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

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

        @Test
        @DisplayName("throws EmptyStackException when popped")
        void throwsExceptionWhenPopped() {
            assertThrows(EmptyStackException.class, () -> stack.pop());
        }

        @Test
        @DisplayName("throws EmptyStackException when peeked")
        void throwsExceptionWhenPeeked() {
            assertThrows(EmptyStackException.class, () -> stack.peek());
        }

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

            String anElement = "an element";

            @BeforeEach
            void pushAnElement() {
                stack.push(anElement);
            }

            @Test
            @DisplayName("it is no longer empty")
            void isNotEmpty() {
                assertFalse(stack.isEmpty());
            }

            @Test
            @DisplayName("returns the element when popped and is empty")
            void returnElementWhenPopped() {
                assertEquals(anElement, stack.pop());
                assertTrue(stack.isEmpty());
            }

            @Test
            @DisplayName("returns the element when peeked but remains not empty")
            void returnElementWhenPeeked() {
                assertEquals(anElement, stack.peek());
                assertFalse(stack.isEmpty());
            }
        }
    }
}

3.8. 重复测试

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

import java.util.logging.Logger;

import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.DisplayName;
import org.junit.jupiter.api.RepeatedTest;
import org.junit.jupiter.api.RepetitionInfo;
import org.junit.jupiter.api.TestInfo;

class RepeatedTestsDemo {

    private Logger logger = // ...

    @BeforeEach
    void beforeEach(TestInfo testInfo, RepetitionInfo repetitionInfo) {
        int currentRepetition = repetitionInfo.getCurrentRepetition();
        int totalRepetitions = repetitionInfo.getTotalRepetitions();
        String methodName = testInfo.getTestMethod().get().getName();
        logger.info(String.format("About to execute repetition %d of %d for %s", //
            currentRepetition, totalRepetitions, methodName));
    }

    @RepeatedTest(10)
    void repeatedTest() {
        // ...
    }

    @RepeatedTest(5)
    void repeatedTestWithRepetitionInfo(RepetitionInfo repetitionInfo) {
        assertEquals(5, repetitionInfo.getTotalRepetitions());
    }

    @RepeatedTest(value = 1, name = "{displayName} {currentRepetition}/{totalRepetitions}")
    @DisplayName("Repeat!")
    void customDisplayName(TestInfo testInfo) {
        assertEquals(testInfo.getDisplayName(), "Repeat! 1/1");
    }

    @RepeatedTest(value = 1, name = RepeatedTest.LONG_DISPLAY_NAME)
    @DisplayName("Details...")
    void customDisplayNameWithLongPattern(TestInfo testInfo) {
        assertEquals(testInfo.getDisplayName(), "Details... :: repetition 1 of 1");
    }

    @RepeatedTest(value = 5, name = "Wiederholung {currentRepetition} von {totalRepetitions}")
    void repeatedTestInGerman() {
        // ...
    }

}

3.9. 参数化测试

@ParameterizedTest
@ValueSource(strings = { "racecar", "radar", "able was I ere I saw elba" })
void palindromes(String candidate) {
    assertTrue(isPalindrome(candidate));
}

4. 引用和引申

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junit.md

junit.md

JUnit5 应用指南

1. 安装

2. JUnit 注解

3. 编写单元测试

3.1. 基本的单元测试类和方法

3.2. 定制测试类和方法的显示名称

3.3. 断言（Assertions）

3.4. 假想（Assumptions）

3.5. 禁用

3.6. 测试条件

操作系统条件

Java 运行时版本条件

系统属性条件

3.7. 嵌套测试

3.8. 重复测试

3.9. 参数化测试

4. 引用和引申

Files

junit.md

Latest commit

History

junit.md

File metadata and controls

JUnit5 应用指南

1. 安装

2. JUnit 注解

3. 编写单元测试

3.1. 基本的单元测试类和方法

3.2. 定制测试类和方法的显示名称

3.3. 断言（Assertions）

3.4. 假想（Assumptions）

3.5. 禁用

3.6. 测试条件

操作系统条件

Java 运行时版本条件

系统属性条件

3.7. 嵌套测试

3.8. 重复测试

3.9. 参数化测试

4. 引用和引申