How to unit test a Java method which calls a different class's static method

Question

I use plain Java and Junit.

   Class A {
       public void tesetMe(arg1, arg2) {
        arg3 = getArg3(arg1);
        B.staticMethod(arg1, arg2, arg3);
   }

   Class B {
     public static void staticMethod(String arg1, String arg2, int arg3) {
        //---
     }
   }

I am testing Class A's testMe method. I want to verify if B's staticMethod is called with specific values of arg1, arg2 and arg3. I cannot have a data member of type Class B. I can use mockito but not powermock or any other library. I do not have a container where I can inject an instance of Class B. I have this like a plain simple java programs calling each other.

Usually, the answer here is that you're testing the wrong thing, and you shouldn't be testing calls to static methods. You should either change how B is organized to make it an instance method, or test the effects that tesetMe is supposed to have, whether it calls staticMethod or not. — Louis Wasserman
– Louis Wasserman, Commented Jan 8, 2023 at 18:01

Mark Ardman · Accepted Answer · 2023-01-08 16:47:21Z

1

So I looked this up and I think this can solve your problem. One can mock a static class by calling mockStatic function, here is a quick example:

MockedStatic<StaticClass> x = Mockito.mockStatic(StaticClass.class);

After that, you can call all the usual functons you would on x variable like that:

x.verify(() -> StaticClass.staticFunction("x"));

I found this Baeldung tutorial and also found a similar question. Hope this helps!

answered Jan 8, 2023 at 16:47

Mark Ardman

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