JUnit5 快速指南

version: junit5

• 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
  • 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

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

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);@BeforeAllstatic void beforeAll() {LOGGER.info("call beforeAll()");}@BeforeEachvoid beforeEach() {LOGGER.info("call beforeEach()");}@Testvoid succeedingTest() {LOGGER.info("call succeedingTest()");}@Testvoid failingTest() {LOGGER.info("call failingTest()");// fail("a failing test");}@Test@Disabled("for demonstration purposes")void skippedTest() {LOGGER.info("call skippedTest()");// not executed}@AfterEachvoid afterEach() {LOGGER.info("call afterEach()");}@AfterAllstatic 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;@BeforeAllpublic static void beforeAll() {person = new Person("John", "Doe");}@Testvoid 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.");}@Testvoid 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()));}@Testvoid 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")));});}@Testvoid exceptionTesting() {Throwable exception = assertThrows(IllegalArgumentException.class, () -> {throw new IllegalArgumentException("a message");});assertEquals("a message", exception.getMessage());}@Testvoid timeoutNotExceeded() {// The following assertion succeeds.assertTimeout(ofMinutes(2), () -> {// Perform task that takes less than 2 minutes.});}@Testvoid timeoutNotExceededWithResult() {// The following assertion succeeds, and returns the supplied object.String actualResult = assertTimeout(ofMinutes(2), () -> {return "a result";});assertEquals("a result", actualResult);}@Testvoid timeoutNotExceededWithMethod() {// The following assertion invokes a method reference and returns an object.String actualGreeting = assertTimeout(ofMinutes(2), AssertionsDemo::greeting);assertEquals("Hello, World!", actualGreeting);}@Testvoid timeoutExceeded() {// The following assertion fails with an error message similar to:// execution exceeded timeout of 10 ms by 91 msassertTimeout(ofMillis(10), () -> {// Simulate task that takes more than 10 ms.Thread.sleep(100);});}@Testvoid timeoutExceededWithPreemptiveTermination() {// The following assertion fails with an error message similar to:// execution timed out after 10 msassertTimeoutPreemptively(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 {@Testvoid testOnlyOnCiServer() {assumeTrue("CI".equals(System.getenv("ENV")));// remainder of test}@Testvoid testOnlyOnDeveloperWorkstation() {assumeTrue("DEV".equals(System.getenv("ENV")),() -> "Aborting test: not on developer workstation");// remainder of test}@Testvoid testInAllEnvironments() {assumingThat("CI".equals(System.getenv("ENV")),() -> {// perform these assertions only on the CI serverassertEquals(2, 2);});// perform these assertions in all environmentsassertEquals("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 {@Testvoid 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@Testvoid testWillBeSkipped() {}@Testvoid 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 {@BeforeEachvoid 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";@BeforeEachvoid 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 = // ...@BeforeEachvoid 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

• Github
• 官方用户手册
• Javadoc
• 版本声明
• 官方示例