目录
JUnit5 快速指南
version: junit5
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 @AfterAllmethods 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)); }