42-单元测试
1. JUnit5 简述
Spring Boot 2.2.0 版本开始引入 JUnit 5 作为单元测试默认库。
作为最新版本的 JUnit 框架，JUnit5 与之前版本的 Junit 框架有很大的不同。由 3 个不同子项目的几个不同模块组成。
JUnit 5 = JUnit Platform + JUnit Jupiter + JUnit Vintage
- 【JUnit Platform】Junit Platform 是在 JVM 上启动测试框架的基础，不仅支持 JUnit 自制的测试引擎，其他测试引擎也都可以接入；
- 【JUnit Jupiter】JUnit Jupiter提供了 JUnit5 的新的编程模型，是 JUnit5 新特性的核心。内部包含了一个测试引擎，用于在 Junit Platform 上运行；
- 【JUnit Vintage】由于 JUint 已经发展多年，为了照顾老的项目，JUnit Vintage 提供了兼容 JUnit4.x、JUnit3.x 的测试引擎。
导入 test-starter，本人学习使用的 2.4.3 的 SpringBoot：
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
查看 Maven-Dependencies：
https://github.com/spring-projects/spring-boot/wiki/Spring-Boot-2.4-Release-Notes
【JUnit 5’s Vintage Engine Removed from spring-boot-starter-test】If you upgrade to Spring Boot 2.4 and see test compilation errors for JUnit classes such as org.junit.Test, this may be because JUnit 5’s vintage engine has been removed from spring-boot-starter-test. The vintage engine allows tests written with JUnit 4 to be run by JUnit 5. If you do not want to migrate your tests to JUnit 5 and wish to continue using JUnit 4, add a dependency on the Vintage Engine, as shown in the following example for Maven:
<dependency>
<groupId>org.junit.vintage</groupId>
<artifactId>junit-vintage-engine</artifactId>
<scope>test</scope>
<exclusions>
<exclusion>
<groupId>org.hamcrest</groupId>
<artifactId>hamcrest-core</artifactId>
</exclusion>
</exclusions>
</dependency>
2. 常用注解
https://junit.org/junit5/docs/current/user-guide/#writing-tests-annotations
| 注解 | 介绍 |
|---|---|
| @Test | 表示方法是测试方法；但是与 JUnit4 的 @Test 不同，他的职责非常单一不能声明任何属性，拓展的测试将会由 Jupiter 提供额外测试 |
| @Timeout | 表示测试方法运行如果超过了指定时间将会返回错误 |
| @Disabled | 表示测试类或测试方法不执行，类似于 JUnit4 中的 @Ignore |
| @DisplayName | 为测试类或者测试方法设置展示名称 |
| @ExtendWith | 为测试类或测试方法提供扩展类引用 @SpringBootTest=xxx+@ExtendWith(SpringExtension.class) |
| @BeforeEach | 表示在每个单元测试之前执行 |
| @AfterEach | 表示在所有单元测试之前执行 |
| @BeforeAll | 表示在所有单元测试之前执行 |
| @AfterAll | 表示在所有单元测试之后执行 |
| @Tag | 表示单元测试类别，类似于 JUnit4 中的 @Categories |
| @RepeatedTest | 表示方法可重复执行 |
| @ParameterizedTest | 表示方法是参数化测试，下方会有详细介绍 |
3. 断言
https://junit.org/junit5/docs/current/user-guide/#writing-tests-assertions
断言（assertions）是测试方法中的核心部分，用来对测试需要满足的条件进行验证。这些断言方法都是 org.junit.jupiter.api.Assertions 的静态方法。
- 简单断言
- 数组断言：通过
assertArrayEquals方法来判断两个对象或原始类型的数组是否相等； - 组合断言：
assertAll方法接受多个org.junit.jupiter.api.Executable函数式接口的实例作为要验证的断言，可以通过 lambda 表达式很容易的提供这些断言； - 异常断言：
Assertions.assertThrows()测试方法的异常情况，配合函数式编程就可以进行使用； - 超时断言：
Assertions.assertTimeout()为测试方法设置了超时时间； - 快速失败：通过
fail方法直接使得测试失败。
class AssertionsDemo {
private final Calculator calculator = new Calculator();
private final Person person = new Person("Jane", "Doe");
@Test
void standardAssertions() {
assertEquals(2, calculator.add(1, 1));
assertEquals(4, calculator.multiply(2, 2),
"The optional failure 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 all
// failures will be reported together.
assertAll("person",
() -> assertEquals("Jane", 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("e"))
);
},
() -> {
// 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() {
Exception exception = assertThrows(ArithmeticException.class, () ->
calculator.divide(1, 0));
assertEquals("/ by zero", 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.
new CountDownLatch(1).await();
});
}
private static String greeting() {
return "Hello, World!";
}
}
4. 前置条件
https://junit.org/junit5/docs/current/user-guide/#writing-tests-assumptions
JUnit 5 中的前置条件 「assumptions(假设)」类似于断言，不同之处在于不满足的断言会使得测试方法失败，而不满足的前置条件只会使得测试方法的执行终止。前置条件可以看成是测试方法执行的前提，当该前提不满足时，就没有继续执行的必要。
class AssumptionsDemo {
private final Calculator calculator = new Calculator();
@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, calculator.divide(4, 2));
});
// perform these assertions in all environments
assertEquals(42, calculator.multiply(6, 7));
}
}
5. 嵌套测试
https://junit.org/junit5/docs/current/user-guide/#writing-tests-nested
补充：内层可以驱动外层的 @Before/After|Each/All，但外层不能驱动内层的。
@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());
}
}
}
}
6. 参数化测试
https://junit.org/junit5/docs/current/user-guide/#writing-tests-parameterized-tests
| 参数化注解 | 简述 |
|---|---|
| @ValueSource | 为参数化测试指定入参来源，支持 8 大基础类以及 String、Class 类型 |
| @NullSource | 表示为参数化测试提供一个 null 的入参 |
| @EnumSource | 表示为参数化测试提供一个枚举入参 |
| @CsvFileSource | 表示读取指定 CSV 文件内容作为参数化测试入参 |
| @MethodSource | 表示读取指定方法的返回值作为参数化测试入参（注意方法返回需要是一个流） |
The following example demonstrates a parameterized test that uses the @ValueSource annotation to specify a String[] as the source of arguments.
@ParameterizedTest
@ValueSource(strings = { "racecar", "radar", "able was I ere I saw elba" })
void palindromes(String candidate) {
assertTrue(StringUtils.isPalindrome(candidate));
}
When executing the above parameterized test method, each invocation will be reported separately. For instance, the ConsoleLauncher will print output similar to the following.
palindromes(String) ✔
├─ [1] candidate=racecar ✔
├─ [2] candidate=radar ✔
└─ [3] candidate=able was I ere I saw elba ✔
If you only need a single parameter, you can return a Stream of instances of the parameter type as demonstrated in the following example.
@ParameterizedTest
@MethodSource("stringProvider")
void testWithExplicitLocalMethodSource(String argument) {
assertNotNull(argument);
}
static Stream<String> stringProvider() {
return Stream.of("apple", "banana");
}
7. 迁移指南
在进行迁移的时候需要注意如下的变化：
- 注解在 org.junit.jupiter.api 包中，断言在 org.junit.jupiter.api.Assertions 类中，前置条件在 org.junit.jupiter.api.Assumptions 类中；
- 把
@Before和@After替换成@BeforeEach和@AfterEach； - 把
@BeforeClass和@AfterClass替换成@BeforeAll和@AfterAll； - 把
@Ignore替换成@Disabled； - 把
@Category替换成@Tag； - 把
@RunWith、@Rule和@ClassRule替换成@ExtendWith。
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