使用 JUnit 4 测试自定义异常的错误代码

Question

我想测试异常的返回代码。这是我的生产代码：

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

以及相应的例外：

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));
  }

这就是您在这里所需要的：

• 您不希望期望该特定异常，因为您想检查它的某些属性
• 你知道你想输入那个特定的 catch 块;因此当调用没有抛出时，你只会失败。
• 你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过载以接收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，您需要将仓鼠匹配器添加到依赖项中。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)声明即可进行@Test注释

Answer 3

扩展 Sergii 的答案，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