java - 用于比较父类(super class)和子类的 Hamcrest 匹配器

Question

我有以下类(class):

abstract class Answer<T> {}
class AnswerInt extends Answer<Integer> {}
class AnswerText extends Answer<String> {}

现在我想在下面的测试中使用 Hamcrest Matcher(这只是简化的示例):

@Test
public void test() {
    Answer a = new AnswerInt(5);
    assertThat(a, is(new AnswerInt(5))); // Compile error
}    

但是我得到了编译错误: The method assertThat(T, Matcher<? super T>) in the type MatcherAssert is not applicable for the arguments (Answer, Matcher<AnswerInt>) .

我理解错误信息，但不明白为什么 assertThat定义为 .. Matcher<? super T> .

是否可以编写混合父类(super class)和子类的断言？

接下来，我想写这样的断言:

Map<String,Answer> answerMap = questionary.getAnswerMap();
assertThat(answerMap, allOf(
    hasEntry("var1", new AnswerInt(5)),
    hasEntry("var2", new AnswerText("foo"))
));

但我遇到了同样的错误。

我使用的是 Hamcrest 1.3 版

Answer 1

如果您使用 Java 8 运行测试，它会编译。对于以前的版本，您必须给编译器一个提示:

@Test
public void test() {
    Answer a = new AnswerInt(5);
    assertThat(a, Matchers.<Answer>is(new AnswerInt(5)));
}