Question

我正在浏览junit ExpectedExceptions' javadoc，我无法理解他们示例中startsWith的来源（在代码中标记为HERE）。我检查了CoreMatcher utility class，但找不到任何静态startsWith方法。

该方法位于何处？

（我显然可以自己写，但这不是重点）

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

    @Test
    public void throwsNullPointerExceptionWithMessage() {
        thrown.expect(NullPointerException.class);
        thrown.expectMessage("happened?");
        thrown.expectMessage(startsWith("What")); //HERE
        throw new NullPointerException("What happened?");
    }
}

Answer 1

import static org.hamcrest.core.StringStartsWith.startsWith;

启用两者

assertThat(msg, startsWith ("what"));

和

ExpectedException.none().expectMessage(startsWith("What")); //HERE

Answer 2

这很可能是Hamcrest Matchers class中的startsWith方法。

Answer 3

查看ExpectedException，我们可以看到定义了两个expectMessage方法，一个是String，一个是Matcher，确实是org.hamcrest.Matcher。

/**
 * Adds to the list of requirements for any thrown exception that it should
 * <em>contain</em> string {@code substring}
 */
public void expectMessage(String substring) {
    expectMessage(containsString(substring));
}

/**
 * Adds {@code matcher} to the list of requirements for the message returned
 * from any thrown exception.
 */
public void expectMessage(Matcher<String> matcher) {
    expect(hasMessage(matcher));
}

JUnit Matcher的声明在哪里#startingWith？

3 个答案: