使用 JUnit 4 测试自定义异常的错误代码

Question

我想测试异常的return代码。这是我的生产代码：

class A {
  try {
    something...
  }
  catch (Exception e)
  {
    throw new MyExceptionClass(INTERNAL_ERROR_CODE, e);
  }
}

以及对应的异常：

class MyExceptionClass extends ... {
  private errorCode;

  public MyExceptionClass(int errorCode){
    this.errorCode = errorCode;
  }

  public getErrorCode(){ 
    return this.errorCode;
  }
}

我的单元测试：

public class AUnitTests{
  @Rule
  public ExpectedException thrown= ExpectedException.none();

  @Test (expected = MyExceptionClass.class, 
  public void whenRunningSomething_shouldThrowMyExceptionWithInternalErrorCode() throws Exception {
      thrown.expect(MyExceptionClass.class);
      ??? expected return code INTERNAL_ERROR_CODE ???

      something();
  }
}

Answer 1

简单：

 @Test 
 public void whenSerialNumberIsEmpty_shouldThrowSerialNumberInvalid() throws Exception {
  try{
     whenRunningSomething_shouldThrowMyExceptionWithInternalErrorCode();     
     fail("should have thrown");
  }
  catch (MyExceptionClass e){
     assertThat(e.getCode(), is(MyExceptionClass.INTERNAL_ERROR_CODE));
  }

这就是您所需要的：

您不想期待那个特定的异常，因为您想要检查它的某些属性
您知道您想要进入那个特定的捕获块；因此，当调用没有抛出
您不需要任何其他检查 - 当该方法抛出任何其他异常时，JUnit 无论如何都会将其报告为错误

Answer 2

只要 thrown.expect 过载接收 Matcher

，您就可以使用 hamcres 匹配器检查它

thrown.expect(CombinableMatcher.both(
           CoreMatchers.is(CoreMatchers.instanceOf(MyExceptionClass.class)))
           .and(Matchers.hasProperty("errorCode", CoreMatchers.is(123))));

请注意，您需要将 hamcrest 匹配器添加到您的依赖项中。 JUnit中包含的核心匹配是不够的。

或者如果您不想使用 CombinableMatcher：

thrown.expect(CoreMatchers.instanceOf(MyExceptionClass.class));
thrown.expect(Matchers.hasProperty("errorCode", CoreMatchers.is(123));

此外，您不需要 (expected = MyExceptionClass.class) 声明 @Test 注释

Answer 3

扩展 Sergii 的回答，您可以通过编写自定义匹配器来进一步清理它。

import org.hamcrest.Description;
import org.hamcrest.TypeSafeMatcher;

public class CustomMatcher extends TypeSafeMatcher<CustomException> {

    public static CustomMatcher hasCode(String item) {
        return new CustomMatcher(item);
    }

    private String foundErrorCode;
    private final String expectedErrorCode;

    private CustomMatcher(String expectedErrorCode) {
        this.expectedErrorCode = expectedErrorCode;
    }

    @Override
    protected boolean matchesSafely(final CustomException exception) {
        foundErrorCode = exception.getErrorCode();
        return foundErrorCode.equalsIgnoreCase(expectedErrorCode);
    }

    @Override
    public void describeTo(Description description) {
        description.appendValue(foundErrorCode)
                .appendText(" was not found instead of ")
                .appendValue(expectedErrorCode);
    }
}

然后可以像这样检查错误代码：

import org.junit.rules.ExpectedException;

public class MyObjTest {

    @Rule
    public ExpectedException thrown = ExpectedException.none();

    @Test
    public void someMethodThatThrowsCustomException() {
        thrown.expect(CustomException.class);
        thrown.expect(CustomMatcher.hasCode("110501"));

        MyObj obj = new MyObj();
        obj.methodThatThrowsCustomException();
    }
}

参考：https://dzone.com/articles/testing-custom-exceptions

使用 JUnit 4 测试自定义异常的错误代码

Test the error code of a custom exception with JUnit 4

java

junit

junit4

junit-rule