JMockit：验证测试的 class 实例的方法调用

Question

I currently have the following code for testing:

public class TestClass {
    @Tested
    private MyClass myClass = new MyClass();

    @Test
    public void test(@Mocked IntWrapper wrapper) {
        new Expectations() {{
            wrapper.value();
            result = 20;
        }};

        myClass.doSomething(wrapper);

        new Verifications() {{
            myClass.larger();
            times = 1;
        }};
    }
}

class IntWrapper {
    public int value() {
        return 0;
    }
}

class MyClass {
    public void doSomething(IntWrapper wrapper) {
        if (wrapper.value() <= 10) {
            smaller();
        } else {
            larger();
        }

    }

    public void larger() {
        System.out.println("Larger than 10");
    }

    public void smaller() {
        System.out.println("Smaller than 10");
    }
}

The test code above will throw an java.lang.NullPointerException in the verification part. Is there something that I am not understanding with regards to the use of the Tested classes? Or are there any ways I can verify method call of unmocked class instances?

Thank you!

Answer 1

JMockit can be finicky. I tend to

• consolidate Verifications into Expectations - just cleaner
• add the class-under-test to the expectations initializer (forcing it to be mocked)
• avoid specifying a constructor with @Tested, use @Injectable as necessary, unless you need a specific ctor.

public class TestClass {
    @Tested
    private MyClass myClass;

    @Test
    public void test(@Mocked IntWrapper wrapper) {
        new Expectations(myClass) {{
            wrapper.value();
            times=1;
            result = 20;

            myClass.larger();
            times=1;
        }};

        myClass.doSomething(wrapper);
    }
}