assertThat(actual).usingRecursiveComparison().ignoringAllOverriddenEquals().isEqualTo(expected) 的奇怪行为

Question

我在 assertj 库中遇到了一个有趣的递归比较行为。 如果比较作为子类的类的对象，则在比较过程中似乎会跳过超类的字段。 这是一个已知问题吗？ 还是我做错了什么？ 下面是一个简单的例子：

import org.junit.Test;
import static org.assertj.core.api.Assertions.assertThat;

public class ExampleTest {

  @Test
  public void test() {
    MyException expected =
            new MyException("Expected text message");
    MyException actual = new MyException("Actual text message"); //values for the field Throwable.detailMessage are different
    assertThat(actual).usingRecursiveComparison().ignoringAllOverriddenEquals().isEqualTo(expected);
  }
}

class MyException extends RuntimeException {

  MyException(String message) {
    super(message);
  }
}

这个测试会在实际不应该通过的时候通过。 actual.getMessage()和expected.getMessage()将显示不同的值。

Answer 1

显然，lib 跳过了从驻留在java.lang超类继承的字段的比较。 由于MyException使用从java.lang.Throwable继承的detailMessage字段，因此它被跳过。 这是来自org.assertj.core.internal.Objects的代码，它似乎对这种行为负责：

/**
   * Returns the declared fields of given class and its superclasses stopping at superclass in <code>java.lang</code>
   * package whose fields are not included.
   *
   * @param clazz the class we want the declared fields.
   * @return the declared fields of given class and its superclasses.
   */
  public static Set<Field> getDeclaredFieldsIncludingInherited(Class<?> clazz) {
    checkNotNull(clazz, "expecting Class parameter not to be null");
    Set<Field> declaredFields = getDeclaredFieldsIgnoringSyntheticAndStatic(clazz);
    // get fields declared in superclass
    Class<?> superclazz = clazz.getSuperclass();
    while (superclazz != null && !superclazz.getName().startsWith("java.lang")) {
      declaredFields.addAll(getDeclaredFieldsIgnoringSyntheticAndStatic(superclazz));
      superclazz = superclazz.getSuperclass();
    }
    return declaredFields;
  }