JUnit5教程(3):_JUnit5断言

你好啊，我是大阳。

本文我们将讨论JUnit5的断言功能。

JUnit 5 断言是使用测试的实际结果验证预期结果。所有JUnit Jupiter 断言都是org.junit.jupiter.Assertions类中的静态方法，方便使用。

有异常的断言将抛出一个AssertionFailedError或它的一个子类。

1 assertEquals() 和 assertNotEquals()

Assertions.assertEquals()用于断言期望值和实际值相等。Assertions.assertEquals()有许多针对不同数据类型的重载方法，例如 int、short、float、char 等。它还支持在测试失败时传递要打印的错误消息。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)

示例：

package cn.dayangshuo.junit5.tests;
import cn.dayangshuo.junit5.Calculator;
import org.junit.jupiter.api.Assertions;
import org.junit.jupiter.api.DisplayName;
import org.junit.jupiter.api.Test;
import java.util.function.Supplier;
/**
 * @author DAYANG
 */
public class CalculatorTests {
    @Test
    @DisplayName("a + b = c")
    void addsTwoNumbers() {
        //测试通过
        Assertions.assertEquals(4, Calculator.add(2, 2));
        //测试失败
        Assertions.assertEquals(3, Calculator.add(2, 2), "Calculator.add(2, 2) 测试失败");
        //测试失败
        Supplier<String> messageSupplier  = () -> "Calculator.add(2, 2) 测试失败";
        Assertions.assertEquals(3, Calculator.add(2, 2), messageSupplier);
    }
}

相反，Assertions.assertNotEquals()方法用于断言期望值和实际值不相等。与assertEquals()相比，assertNotEquals()不包含针对不同数据类型的重载方法，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)

示例：

@Test
@DisplayName("a + b = c")
void test() {
  //测试通过
  Assertions.assertNotEquals(3, Calculator.add(2, 2));
  //测试失败
  Assertions.assertNotEquals(4, Calculator.add(2, 2), "Calculator.add(2, 2) test failed");
  //测试失败
  Supplier<String> messageSupplier = () -> "Calculator.add(2, 2) test failed";
  Assertions.assertNotEquals(4, Calculator.add(2, 2), messageSupplier);
}

2 assertArrayEquals()

assertArrayEquals() 方法断言预期数组和实际数组相等。

它还具有针对不同数据类型的重载方法，例如 boolean[]、char[]、int[] 等，还支持在测试失败时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)

3 assertIterableEquals()

它断言预期的和实际的可迭代对象是完全相等的。完全相等意味着集合中元素的数量和顺序必须相同，迭代的元素必须相等。

它还具有三个重载方法。

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)

4 assertLinesMatch()

它断言预期的字符串列表与实际列表匹配。

5 assertNotNull() 和 assertNull()

assertNotNull() 断言实际不为空。相反，assertNull()方法断言实际是null。两者都有三个重载方法:

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)

6 assertNotSame() 和 assertSame()

assertNotSame()断言预期和实际的不引用同一个对象。 assertSame() 方法断言预期和实际引用完全相同的对象。两者都有三个重载方法:

public static void assertNotSame(Object expected, Object actual)
public static void assertNotSame(Object expected, Object actual, String message)
public static void assertNotSame(Object expected, Object actual, Supplier<> messageSupplier)

public static void assertSame(Object expected, Object actual)
public static void assertSame(Object expected, Object actual, String message)
public static void assertSame(Object expected, Object actual, Supplier<String> messageSupplier)

7 assertTimeout()

它们是用于测试长时间运行的任务，如果测试任务花费的时间超过指定的持续时间，则测试将失败。

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)

示例：

@Test
void testCase() {
  Assertions.assertTimeout(Duration.ofMinutes(1), () -> {
    return "result";
  });
  Assertions.assertTimeout(Duration.ofMillis(100), () -> {
    Thread.sleep(200);
    return "result";
  });
  Assertions.assertTimeoutPreemptively(Duration.ofMillis(100), () -> {
    Thread.sleep(200);
    return "result";
  });
}

8 assertTrue() and assertFalse()

assertTrue()断言提供的条件为真。相反，assertFalse()断言提供的条件为false。

两者都有以下重载方法：

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)

9 assertThrows()

assetThrows()断言提供的

Executable

执行会引发

expectedType

异常并返回异常

//重载方法
public static <T extends Throwable> T assertThrows(Class<T> expectedType, Executable executable)
//示例  
@Test
void testCase() {
    Throwable exception = Assertions.assertThrows(IllegalArgumentException.class, () -> {
        throw new IllegalArgumentException("error message");
    });
}

10 fail()

*fail()*方法指未通过测试。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";
    }
}