JUnit5 断言示例

原文： 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类中的静态方法。

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()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：

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);
}

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。

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

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：

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。

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) 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。

>>>>
>> 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。

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()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。

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。

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()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：

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

它断言所提供的Executable的执行将引发expectedType的异常并返回该异常。

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()方法仅使测试失败。 它具有以下重载方法：

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)

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";
    }
}

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