使用 junit @Rule，expectCause（）和 hamcrest matchers

unit-testing java maven junit

2022-09-01 14:57:02

我有一个测试：

@Rule
public ExpectedException thrown = ExpectedException.none();
...
@Test
public void testMethod()
{
    final String error = "error message";
    Throwable expectedCause = new IllegalStateException(error);
    thrown.expectCause(org.hamcrest.Matchers.<Throwable>equalTo(expectedCause));
    someServiceThatTrowsException.foo();
}

当通过mvn测试方法运行时，我得到错误：

java.lang.NoSuchMethodError： org.junit.rules.ExpectedException.expectCause（Lorg/hamcrest/Matcher;）V

测试编译正常。

请帮帮我，无法理解异常的原因如何测试？

答案 1

试试这个方法：

@Rule public ExpectedException thrown = ExpectedException.none();

@Test public void testMethod() throws Throwable {
    final String error = "error message";
    Throwable expectedCause = new IllegalStateException(error);
    thrown.expectCause(IsEqual.equalTo(expectedCause));
    throw new RuntimeException(expectedCause);
}

考虑不要通过等于来检查原因，而是通过IsInstanceOf和/或在必要时压缩异常消息。通过等值比较原因，检查堆栈跟踪，这可能比您要测试/检查的更多。例如：

@Rule public ExpectedException thrown = ExpectedException.none();

@Test public void testMethod() throws Throwable {
    final String error = "error message";
    thrown.expectCause(IsInstanceOf.<Throwable>instanceOf(IllegalStateException.class));
    thrown.expectMessage(error);
    throw new RuntimeException(new IllegalStateException(error));
}

答案 2

使用静态导入并检查类和原因异常的消息，更简短一点：

import static org.hamcrest.Matchers.allOf;
import static org.hamcrest.Matchers.hasProperty;
import static org.hamcrest.Matchers.instanceOf;
import static org.hamcrest.Matchers.is;
import static org.junit.Assert.assertThat;

@Test
public void testThatThrowsNiceExceptionWithCauseAndMessages(){

     expectedException.expect(RuntimeException.class );
     expectedException.expectMessage("Exception message");                                           
     expectedException.expectCause(allOf(instanceOf(IllegalStateException.class),
                                        hasProperty("message", is("Cause message"))) );

     throw new RuntimeException("Exception message", new IllegalStateException("Cause message"));
}

您甚至可以使用 hasProperty 匹配器来断言嵌套原因或测试“getLocalizedMessage”方法。

使用 junit @Rule，expectCause（） 和 hamcrest matchers

使用 junit @Rule，expectCause（）和 hamcrest matchers