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JUnit5 应用指南

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:
img

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));
}

4. 引用和引申