How could I test ClassNotFoundException using Mockito?

StackOverflow https://stackoverflow.com/questions/20986195

  •  25-09-2022
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سؤال

I'm running unit test on the following class:

public class FileClass {

    public void funcB() {
        try {
            throw new ClassNotFoundException();
        }
        catch( ClassNotFoundException e ) {

        }
    }
}

Using Mockito code as shown below:

public class TestFileClass {

    @Test(expected=ClassNotFoundException.class)
    public void testFuncB() {
        FileClass fc = Mockito.spy(new FileClass());
        fc.funcB();
    }

}

But the test were failed due to following error:

java.lang.AssertionError: Expected exception: java.lang.ClassNotFoundException
    at org.junit.internal.runners.statements.ExpectException.evaluate(ExpectException.java:35)
    at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:28)
    at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:263)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:68)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:47)
    at org.junit.runners.ParentRunner$3.run(ParentRunner.java:231)
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:60)
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:229)
    at org.junit.runners.ParentRunner.access$000(ParentRunner.java:50)
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:222)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:300)
    at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:50)
    at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:467)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:197)

I did also try on PowerMockito but failed again. Any clue with this error? It seems to me that I can't run any test on ClassNotFoundException?

هل كانت مفيدة؟

المحلول 2

The method funcB() should throw the exception, not catch it. The code bellow and test work fine:

public class FileClass {

public void funcB() throws ClassNotFoundException {
    //try {
        throw new ClassNotFoundException();
    //} catch ( ClassNotFoundException e) {

    //}
}

}

Mockito test:

public class TestFileClass {

@Test(expected = ClassNotFoundException.class)
public void testFuncB() throws ClassNotFoundException {
    FileClass fc = Mockito.spy(new FileClass());
    fc.funcB();
}

}

نصائح أخرى

funcB is not throwing the exception because you are catching it within funcB's body.

I think that describe way of testing exception (expected annotation in @Test) is not the most elegant solution - it break given/when/then convention

The best choice is catch-exception library

http://code.google.com/p/catch-exception/

catch-exception in nice. But the assertj (http://joel-costigliola.github.io/assertj/) has much better support for exception checking

assertThatThrownBy(new DummyService()::someMethod) 
            .isInstanceOf(RuntimeException.class)
            .hasMessage("Runtime exception occurred")
            .hasNoCause();
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