JUnit5 斷言幫助用測試用例的實際輸出來驗證期望的輸出。為簡單起見，所有 JUnit Jupiter 斷言是org.junit.jupiter.Assertions類中的靜態方法。
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()斷言期望值等於實際值。 assertEquals()針對不同的數據類型（例如， int，short，float，char等。它還支持傳遞的錯誤消息，以防萬一測試失敗。 例如：
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)
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); }
類似地，Assertions.assertNotEquals()方法用於斷言期望值不等於實際值。 與assertEquals()相比，assertNotEquals()不會針對不同的數據類型重載方法，而僅接受Object。
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)
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
與assertEquals()相似，assertArrayEquals()對數組執行相同的操作，即斷言期望數組等於實際數組。它還具有針對不同數據類型的重載方法，例如boolean[]，char[]，int[]等。它還支持在測試失敗的情況下傳遞要打印的錯誤消息。 例如：
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)
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
它斷言期望和實際的可迭代項高度相等。 高度相等意味着集合中元素的數量和順序必須相同； 以及迭代元素必須相等。
它還有 3 種重載方法。
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)
@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
它斷言期望的字符串列表與實際列表相匹配。 將一個字符串與另一個字符串匹配的邏輯是：
- 檢查expected.equals(actual) –如果是，則繼續下一對
- 否則將expected視為正則表達式，並通過String.matches(String) 檢查–如果是，則繼續下一對
- 否則檢查expected行是否為快進標記，如果是，則相應地應用快速前行並轉到 1。
有效的快進標記是以>>開頭和結尾並且至少包含 4 個字符的字符串。 快進文字之間的任何字符都將被丟棄。
>>>> >> stacktrace >> >> single line, non Integer.parse()-able comment >>
Assertions.assertNotNull()和Assertions.assertNull()示例
assertNotNull()斷言實際值不為空。 類似地，assertNull()方法斷言實際值為空。 兩者都有三種重載方法。
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)
@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()斷言預期和實際不引用同一對象。 同樣，assertSame()方法斷言，預期和實際引用完全相同的對象。 兩者都有三種重載方法。
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)
@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()均用於測試長時間運行的任務。 如果測試用例中的給定任務花費的時間超過指定的持續時間，則測試將失敗。
兩種方法之間唯一的區別是assertTimeoutPreemptively()中的設置，如果超過超時，Executable或ThrowingSupplier的執行將被搶先中止。 在assertTimeout()的情況下，不會中斷Executable或ThrowingSupplier。
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)
@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()斷言BooleanSupplier提供的條件為真。 類似地，assertFalse()斷言提供的條件為假。 它具有以下重載方法：
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)
@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
它斷言所提供的Executable的執行將引發expectedType的異常並返回該異常。
public static <T extends Throwable> T assertThrows(Class<T> expectedType, Executable executable)
@Test void testCase() { Throwable exception = Assertions.assertThrows(IllegalArgumentException.class, () -> { throw new IllegalArgumentException("error message"); }); }
Assertions.fail()示例
fail()方法僅使測試失敗。 它具有以下重載方法：
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)