Jmockit mocking issue

I am new to Junit and Jmockit . I wrote an example and want to test that using mocking, but i was stuck with an error . Please kindly help.

public class First {

public static int square(int number) {

    int result = number * number;
    return result;
}

}

public class Second {

public static void main(String[] args) {

    int number = 5;

    number = new Second().xi(number, number);
    System.out.println(number);
}

public int xi(int number, int number1) {
    number = First.square(number) + First.square(number1);
    return number;

}

}

public class SecondTest {

Second second = new Second();

@Test
public void testXi() {
    new Expectations() {

        {

            First.square(5);
            result = 25;
        }

    };
    int mk = second.xi(5, 5);
    assertEquals(50, mk);
}

}

When I tried to run this SecondTest.java then i got the following error.

java.lang.IllegalStateException: Missing invocation to mocked type at this point; please make sure such invocations appear only after the declaration of a suitable mock field or parameter at SecondTest$1.(SecondTest.java:17) at SecondTest.testXi(SecondTest.java:12) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at java.lang.reflect.Method.invoke(Method.java:606) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at java.lang.reflect.Method.invoke(Method.java:606) at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:86) at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38) at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:459) at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:675) at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:382) at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:192)

I searched a lot but couldnt find any error in the code. Thanks in advance