• 08-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;
    • @Before@After 替换成 @BeforeEach@AfterEach
    • @BeforeClass@AfterClass 替换成 @BeforeAll@AfterAll
    • @Ignore 替换成 @Disabled
    • @Category 替换成 @Tag
    • @RunWith@Rule@ClassRule 替换成 @ExtendWith
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  • 原文地址:https://www.cnblogs.com/liujiaqi1101/p/15269840.html
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