JUnit5 断言示例 · HowToDoInJava 中文系列教程

# JUnit5 断言示例 > 原文： [https://howtodoinjava.com/junit5/junit-5-assertions-examples/](https://howtodoinjava.com/junit5/junit-5-assertions-examples/) **JUnit5 断言**帮助用测试用例的实际输出来验证期望的输出。为简单起见，所有 **JUnit Jupiter 断言**是[`org.junit.jupiter.Assertions`](http://junit.org/junit5/docs/current/api/org/junit/jupiter/api/Assertions.html)类中的静态方法。 ```java Table of Contents Assertions.assertEquals() and Assertions.assertNotEquals() Assertions.assertArrayEquals() Assertions.assertIterableEquals() Assertions.assertLinesMatch() Assertions.assertNotNull() and Assertions.assertNull() Assertions.assertNotSame() and Assertions.assertSame() Assertions.assertTimeout() and Assertions.assertTimeoutPreemptively() Assertions.assertTrue() and Assertions.assertFalse() Assertions.assertThrows() Assertions.fail() ``` ## `Assertions.assertEquals()`和`Assertions.assertNotEquals()`示例使用`Assertions.assertEquals()`断言**期望值等于实际值**。 `assertEquals()`针对不同的数据类型（例如， `int`，`short`，`float`，`char`等。它还支持传递传递的错误消息，以防万一测试失败。例如： ```java public static void assertEquals(int expected, int actual) public static void assertEquals(int expected, int actual, String message) public static void assertEquals(int expected, int actual, Supplier<String< messageSupplier) ``` ```java void testCase() { //Test will pass Assertions.assertEquals(4, Calculator.add(2, 2)); //Test will fail Assertions.assertEquals(3, Calculator.add(2, 2), "Calculator.add(2, 2) test failed"); //Test will fail Supplier<String> messageSupplier = ()-> "Calculator.add(2, 2) test failed"; Assertions.assertEquals(3, Calculator.add(2, 2), messageSupplier); } ``` 类似地，`Assertions.assertNotEquals()`方法用于断言**期望值不等于实际值**。与`assertEquals()`相比，`assertNotEquals()`不会针对不同的数据类型重载方法，而仅接受`Object`。 ```java public static void assertNotEquals(Object expected, Object actual) public static void assertNotEquals(Object expected, Object actual, String message) public static void assertNotEquals(Object expected, Object actual, Supplier<String> messageSupplier) ``` ```java void testCase() { //Test will pass Assertions.assertNotEquals(3, Calculator.add(2, 2)); //Test will fail Assertions.assertNotEquals(4, Calculator.add(2, 2), "Calculator.add(2, 2) test failed"); //Test will fail Supplier<String> messageSupplier = ()-> "Calculator.add(2, 2) test failed"; Assertions.assertNotEquals(4, Calculator.add(2, 2), messageSupplier); } ``` ## `Assertions.assertArrayEquals()`示例与`assertEquals()`相似，`assertArrayEquals()`对数组执行相同的操作，即断言**期望数组等于实际数组**。它还具有针对不同数据类型的重载方法，例如`boolean[]`，`char[]`，`int[]`等。它还支持在测试失败的情况下传递要打印的错误消息。例如： ```java public static void assertArrayEquals(int[] expected, int[] actual) public static void assertArrayEquals(int[] expected, int[] actual, String message) public static void assertArrayEquals(int[] expected, int[] actual, Supplier<String> messageSupplier) ``` ```java void testCase() { //Test will pass Assertions.assertArrayEquals(new int[]{1,2,3}, new int[]{1,2,3}, "Array Equal Test"); //Test will fail because element order is different Assertions.assertArrayEquals(new int[]{1,2,3}, new int[]{1,3,2}, "Array Equal Test"); //Test will fail because number of elements are different Assertions.assertArrayEquals(new int[]{1,2,3}, new int[]{1,2,3,4}, "Array Equal Test"); } ``` ## `Assertions.assertIterableEquals()`示例它断言**期望和实际的可迭代项高度相等**。高度相等意味着集合中元素的数量和顺序必须相同；以及迭代元素必须相等。它还有 3 种重载方法。 ```java public static void assertIterableEquals(Iterable<?> expected, Iterable> actual) public static void assertIterableEquals(Iterable<?> expected, Iterable> actual, String message) public static void assertIterableEquals(Iterable<?> expected, Iterable> actual, Supplier<String> messageSupplier) ``` ```java @Test void testCase() { Iterable<Integer> listOne = new ArrayList<>(Arrays.asList(1,2,3,4)); Iterable<Integer> listTwo = new ArrayList<>(Arrays.asList(1,2,3,4)); Iterable<Integer> listThree = new ArrayList<>(Arrays.asList(1,2,3)); Iterable<Integer> listFour = new ArrayList<>(Arrays.asList(1,2,4,3)); //Test will pass Assertions.assertIterableEquals(listOne, listTwo); //Test will fail Assertions.assertIterableEquals(listOne, listThree); //Test will fail Assertions.assertIterableEquals(listOne, listFour); } ``` ## `Assertions.assertLinesMatch()`示例它断言**期望的字符串列表与实际列表**相匹配。将一个字符串与另一个字符串匹配的逻辑是： 1. 检查`expected.equals(actual)` –如果是，则继续下一对 2. 否则将`expected`视为正则表达式，并通过 [`String.matches(String)`](https://docs.oracle.com/javase/8/docs/api/java/lang/String.html#matches-java.lang.String-) 检查–如果是，则继续下一对 3. 否则检查`expected`行是否为快进标记，如果是，则相应地应用快速前行并转到 1。有效的快进标记是以`>>`开头和结尾并且至少包含 4 个字符的字符串。快进文字之间的任何字符都将被丢弃。 ```java >>>> >> stacktrace >> >> single line, non Integer.parse()-able comment >> ``` ## `Assertions.assertNotNull()`和`Assertions.assertNull()`示例 `assertNotNull()`断言**实际值不为空**。类似地，`assertNull()`方法断言**实际值为空**。两者都有三种重载方法。 ```java public static void assertNotNull(Object actual) public static void assertNotNull(Object actual, String message) public static void assertNotNull(Object actual, Supplier<String> messageSupplier) public static void assertEquals(Object actual) public static void assertEquals(Object actual, String message) public static void assertEquals(Object actual, Supplier<String> messageSupplier) ``` ```java @Test void testCase() { String nullString = null; String notNullString = "howtodoinjava.com"; //Test will pass Assertions.assertNotNull(notNullString); //Test will fail Assertions.assertNotNull(nullString); //Test will pass Assertions.assertNull(nullString); // Test will fail Assertions.assertNull(notNullString); } ``` ## `Assertions.assertNotSame()`和`Assertions.assertSame()`示例 `assertNotSame()`断言**预期和实际不引用同一对象**。同样，`assertSame()`方法断言，**预期和实际引用完全相同的对象**。两者都有三种重载方法。 ```java public static void assertNotSame(Object actual) public static void assertNotSame(Object actual, String message) public static void assertNotSame(Object actual, Supplier<> messageSupplier) public static void assertSame(Object actual) public static void assertSame(Object actual, String message) public static void assertSame(Object actual, Supplier<String> messageSupplier) ``` ```java @Test void testCase() { String originalObject = "howtodoinjava.com"; String cloneObject = originalObject; String otherObject = "example.com"; //Test will pass Assertions.assertNotSame(originalObject, otherObject); //Test will fail Assertions.assertNotSame(originalObject, cloneObject); //Test will pass Assertions.assertSame(originalObject, cloneObject); // Test will fail Assertions.assertSame(originalObject, otherObject); } ``` ## `Assertions.assertTimeout()`和`Assertions.assertTimeoutPreemptively()`示例 `assertTimeout()`和`assertTimeoutPreemptively()`均用于测试长时间运行的任务。如果测试用例中的给定任务花费的时间超过指定的持续时间，则测试将失败。两种方法之间唯一的区别是`assertTimeoutPreemptively()`中的设置，如果超过超时，`Executable`或`ThrowingSupplier`的执行将被抢先中止。在`assertTimeout()`的情况下，不会中断`Executable`或`ThrowingSupplier`。 ```java public static void assertTimeout(Duration timeout, Executable executable) public static void assertTimeout(Duration timeout, Executable executable, String message) public static void assertTimeout(Duration timeout, Executable executable, Supplier<String> messageSupplier) public static void assertTimeout(Duration timeout, ThrowingSupplier<T> supplier, String message) public static void assertTimeout(Duration timeout, ThrowingSupplier<T> supplier, Supplier<String> messageSupplier) ``` ```java @Test void testCase() { //This will pass Assertions.assertTimeout(Duration.ofMinutes(1), () -> { return "result"; }); //This will fail Assertions.assertTimeout(Duration.ofMillis(100), () -> { Thread.sleep(200); return "result"; }); //This will fail Assertions.assertTimeoutPreemptively(Duration.ofMillis(100), () -> { Thread.sleep(200); return "result"; }); } ``` ## `Assertions.assertTrue()`和`Assertions.assertFalse()`示例 `assertTrue()`断言`BooleanSupplier`提供的条件为真。类似地，`assertFalse()`断言**提供的条件为假**。它具有以下重载方法： ```java public static void assertTrue(boolean condition) public static void assertTrue(boolean condition, String message) public static void assertTrue(boolean condition, Supplier<String> messageSupplier) public static void assertTrue(BooleanSupplier booleanSupplier) public static void assertTrue(BooleanSupplier booleanSupplier, String message) public static void assertTrue(BooleanSupplier booleanSupplier, Supplier<String> messageSupplier) public static void assertFalse(boolean condition) public static void assertFalse(boolean condition, String message) public static void assertFalse(boolean condition, Supplier<String> messageSupplier) public static void assertFalse(BooleanSupplier booleanSupplier) public static void assertFalse(BooleanSupplier booleanSupplier, String message) public static void assertFalse(BooleanSupplier booleanSupplier, Supplier<String> messageSupplier) ``` ```java @Test void testCase() { boolean trueBool = true; boolean falseBool = false; Assertions.assertTrue(trueBool); Assertions.assertTrue(falseBool, "test execution message"); Assertions.assertTrue(falseBool, AppTest::message); Assertions.assertTrue(AppTest::getResult, AppTest::message); Assertions.assertFalse(falseBool); Assertions.assertFalse(trueBool, "test execution message"); Assertions.assertFalse(trueBool, AppTest::message); Assertions.assertFalse(AppTest::getResult, AppTest::message); } private static String message () { return "Test execution result"; } private static boolean getResult () { return true; } ``` ## `Assertions.assertThrows()`示例它断言所提供的`Executable`的执行将引发`expectedType`的异常并返回该异常。 ```java public static <T extends Throwable> T assertThrows(Class<T> expectedType, Executable executable) ``` ```java @Test void testCase() { Throwable exception = Assertions.assertThrows(IllegalArgumentException.class, () -> { throw new IllegalArgumentException("error message"); }); } ``` ## `Assertions.fail()`示例 `fail()`方法仅使测试失败。它具有以下重载方法： ```java public static void fail(String message) public static void fail(Throwable cause) public static void fail(String message, Throwable cause) public static void fail(Supplier<String> messageSupplier) ``` ```java public class AppTest { @Test void testCase() { Assertions.fail("not found good reason to pass"); Assertions.fail(AppTest::message); } private static String message () { return "not found good reason to pass"; } } ``` 将我的问题放在评论部分。学习愉快！