AssertJ：使用方法 assertThatThrownBy 时如何返回实际异常

Question

我正在从 JUnit 5 和 Hamcrest 断言迁移到 AssertJ，但我无法找出从可执行文件中提取实际异常的正确方法。 这是一个 JUnit/Hamcrest 示例：

var result = assertThrows(MyException.class, () -> this.objectUnderTest.someMethod(param1, param2, param3));
assertThat(result.getError().getErrorCode(), equalTo(someValue));
assertThat(result.getError().getDescription(), equalTo("someString"));

我想要的是smth。 喜欢（AssertJ）

var result = assertThatThrownBy(() -> this.objectUnderTest.someMethod(param1, param2, param3))
 .isInstanceOf(MyException.class);
assertThat(result.getError().getErrorCode(), equalTo(someValue));
assertThat(result.getError().getDescription(), equalTo("someString"));

但是从 AssertJ 版本3.21.0 ， assertThatThrownBy方法给了我一个AbstractThrowableAssert<?,? extends Throwable> AbstractThrowableAssert<?,? extends Throwable> class 并且我找不到任何可以给我然后MyException实例的方法。 所以现在我最终使用了另一种方法并手动转换为MyException ：

Throwable throwable = Assertions.catchThrowable(() -> this.objectUnderTest.doFilterInternal(param1, param2, param3));
MyException exception = (MyException) throwable;
assertThat(exception.getError().getErrorCode(), equalTo(someValue));
assertThat(exception.getError().getDescription(), equalTo("someString"));

Answer 1

AssertJ 提供了两个 styles 用于检查自定义异常：

• 带有catchThrowableOfType的BDD 样式
• 带有assertThatExceptionOfType的单语句样式

保持示例的风格，您可以使用catchThrowable编写以下内容：

Throwable throwable = catchThrowable(() -> this.objectUnderTest.someMethod(param1, param2, param3));

assertThat(throwable)
  .asInstanceOf(InstanceOfAssertFactories.throwable(MyException.class))
  .extracting(MyException::getError)
  .returns(1, from(Error::getErrorCode))
  .returns("something", from(Error::getDescription));

或者，使用catchThrowableOfType ：

MyException exception = catchThrowableOfType(() -> this.objectUnderTest.someMethod(param1, param2, param3), MyException.class);

assertThat(exception)
  .extracting(MyException::getError)
  .returns(1, from(Error::getErrorCode))
  .returns("something", from(Error::getDescription));

Answer 2

var result = assertThatThrownBy(() -> this.objectUnderTest.someMethod(param1, param2, param3)).isInstanceOf(MyException.class); assertThat(result.getError().getErrorCode(), equalTo(someValue)); assertThat(result.getError().getDescription(), equalTo("someString"));

AssertJ 方式如下：

assertThatExceptionOfType(MyException.class)
        .isThrownBy(() -> this.objectUnderTest.someMethod(param1, param2, param3))
        .satisfies(ex -> assertThat(ex.getError().getErrorCode()).isEqualTo(someValue));