我怎么能用Mockito测试ClassNotFoundException？

我在下面的课上运行单元测试:

public class FileClass {

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

        }
    }
}

使用Mockito代码如下所示:

public class TestFileClass {

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

}

但由于以下错误,测试失败:

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)

我也试过PowerMockito但又失败了.有这个错误的任何线索？在我看来,我不能进行任何测试ClassNotFoundException？