如何使用JUnit来测试某些代码是否抛出异常？
我当然可以这样做：
@Test
public void testFooThrowsIndexOutOfBoundsException() {
boolean thrown = false;
try {
foo.doStuff();
} catch (IndexOutOfBoundsException e) {
thrown = true;
}
assertTrue(thrown);
}
我记得，对于这类情况，有一个注释或Assert.xyz之类的东西远没有JUnit那么笨拙，更符合JUnit的精神。
当前回答
在我的例子中，我总是从数据库中得到RuntimeException，但消息不同。需要分别处理异常。以下是我测试它的方法：
@Test
public void testThrowsExceptionWhenWrongSku() {
// Given
String articleSimpleSku = "999-999";
int amountOfTransactions = 1;
Exception exception = null;
// When
try {
createNInboundTransactionsForSku(amountOfTransactions, articleSimpleSku);
} catch (RuntimeException e) {
exception = e;
}
// Then
shouldValidateThrowsExceptionWithMessage(exception, MESSAGE_NON_EXISTENT_SKU);
}
private void shouldValidateThrowsExceptionWithMessage(final Exception e, final String message) {
assertNotNull(e);
assertTrue(e.getMessage().contains(message));
}
其他回答
在我的例子中，我总是从数据库中得到RuntimeException，但消息不同。需要分别处理异常。以下是我测试它的方法：
@Test
public void testThrowsExceptionWhenWrongSku() {
// Given
String articleSimpleSku = "999-999";
int amountOfTransactions = 1;
Exception exception = null;
// When
try {
createNInboundTransactionsForSku(amountOfTransactions, articleSimpleSku);
} catch (RuntimeException e) {
exception = e;
}
// Then
shouldValidateThrowsExceptionWithMessage(exception, MESSAGE_NON_EXISTENT_SKU);
}
private void shouldValidateThrowsExceptionWithMessage(final Exception e, final String message) {
assertNotNull(e);
assertTrue(e.getMessage().contains(message));
}
我想评论一下这个问题的解决方案，它避免了任何与异常相关的JUnit代码。
我使用assertTrue（布尔值）和try/catch组合来查找要抛出的预期异常。下面是一个示例：
public void testConstructor() {
boolean expectedExceptionThrown;
try {
// Call constructor with bad arguments
double a = 1;
double b = 2;
double c = a + b; // In my example, this is an invalid option for c
new Triangle(a, b, c);
expectedExceptionThrown = false; // because it successfully constructed the object
}
catch(IllegalArgumentException e) {
expectedExceptionThrown = true; // because I'm in this catch block
}
catch(Exception e) {
expectedExceptionThrown = false; // because it threw an exception but not the one expected
}
assertTrue(expectedExceptionThrown);
}
我使用Java 8 lambdas的解决方案：
public static <T extends Throwable> T assertThrows(Class<T> expected, ThrowingRunnable action) throws Throwable {
try {
action.run();
Assert.fail("Did not throw expected " + expected.getSimpleName());
return null; // never actually
} catch (Throwable actual) {
if (!expected.isAssignableFrom(actual.getClass())) { // runtime '!(actual instanceof expected)'
System.err.println("Threw " + actual.getClass().getSimpleName()
+ ", which is not a subtype of expected "
+ expected.getSimpleName());
throw actual; // throw the unexpected Throwable for maximum transparency
} else {
return (T) actual; // return the expected Throwable for further examination
}
}
}
您必须定义FunctionalInterface，因为Runnable没有声明所需的抛出。
@FunctionalInterface
public interface ThrowingRunnable {
void run() throws Throwable;
}
方法如下：
class CustomException extends Exception {
public final String message;
public CustomException(final String message) { this.message = message;}
}
CustomException e = assertThrows(CustomException.class, () -> {
throw new CustomException("Lorem Ipsum");
});
assertEquals("Lorem Ipsum", e.message);
JUnit框架具有assertThrows（）方法：
ArithmeticException exception = assertThrows(ArithmeticException.class, () ->
calculator.divide(1, 0));
assertEquals("/ by zero", exception.getMessage());
对于JUnit 5，它位于org.unit.jupiter.api.Assertions类中；对于JUnit 4.13，它位于org.JUnit.Assert类中；对于JUnit4的早期版本：只需将org.JUnit.jupiter:junitjupiterapi上的引用添加到项目中，就可以从JUnit5获得非常好的工作版本。
我建议库assertj核心处理junit测试中的异常
在java 8中，如下所示：
//given
//when
Throwable throwable = catchThrowable(() -> anyService.anyMethod(object));
//then
AnyException anyException = (AnyException) throwable;
assertThat(anyException.getMessage()).isEqualTo("........");
assertThat(exception.getCode()).isEqualTo(".......);
