java - JUnit Matcher#startsWith 的声明在哪里？

Question

我正在浏览junitExpectedExceptions的 javadoc，但我无法理解startsWith他们示例中的 来自哪里（在代码中标记为 HERE）。我检查了CoreMatcher实用程序类，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;

使两者

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

和

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

Answer 2

这很可能是startsWith来自 Hamcrestorg.hamcrest.Matchers类的方法。

Answer 3

查看ExpectedException，我们可以看到定义了两个 expectMessage 方法，一个 String 和一个 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));
}