Alternatives to mock an static method

Question

I am developing a desktop application, I want to test the method foo of MyClass and I have the following scenario:
MyClass:

import package.MainWindow;

public class MyClass{

    public int foo(){
        //some logic
        // . . .
        boolean result = getResult();
        if (result) {
            MainWindow.printInMain("Success");
            return 1;
        } else {
            MainWindow.printInMain("Fail: " + getCommentsAsString());
            return 2;
        }
    }
}

Then, I have MainWindow with its static method printInMain:

public class MainWindow{

    private static JTextArea jTextArea;

    MainWindow(){
        jTextArea = new JTextArea();
    }

    public static void printInMain(String string) {
        jTextArea.append(string + "\n");
        try {
           jTextArea.setCaretPosition(jTextArea.
             getLineStartOffset(jTextArea.getLineCount() - 1));
        } catch (BadLocationException e) {
            e.printStackTrace();
        }
    }
}

MainWindow is the interface of my program, and jTextArea is the swing component that is printing the information that I send from MyClass.foo().
Now I am testing foo() with jUnit, and I don't need the graphic user interface to test it. The test is pretty straight forward, but I get a nullPointer exception when calling the printing method because MainWindow hasn´t been instantiated so jTextArea is null.
My question is, is there any clean way of avoiding this error of being thrown?
I am using mockito and as far as I know, static methods cannot be mocked.
In some other cases, I could have done something like this:

MainWindow mainWindow = Mockito.mock(MainWindow.class);

But MainWindow is not being set in MyClass, so this is not very useful either.
Finally I came up with a workaround that does what I want, but it's not very clean. Basically I have declared a static boolean flag printText and set it as false at the very beginning of MainWindow, and I am setting it as true in the class constructor. Then, in printInMain I only print if this flag is true, which will only happen if this class has been previously instantiated.
This approach works but I was wondering whether there is a better solution than this, maybe using Mockito or some other mocking or testing techniques, as I am not very familiar with them.
I don't think this is a very good option because I am adding some code in the application just to make the test work, and the test should adapt to my code, not the code to my test.

score 1 · Accepted Answer · answered May 04 '15 at 10:21

1

While putting a null pointer check in the static method would avoid the NPE being thrown; it it a bit of a code smell.

I would suggest that the jTextArea be declared as non-static which in turns implies that the printInMain method would also be non-static. This then leads to it being able to be mocked.

answered May 04 '15 at 10:21

Brett Walker

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Thanks for the answer Brett. I though about this null pointer check when I was finishing writing the question, I will probably add it. About the `jTextArea` being non-static, the problem is that many classes call only this method of the main window, and there is only one main window, so making it non-static means that I will have to pass the instance of `MainWindow` to every class that I want to let print in it, am I right? – Juan May 04 '15 at 10:35
Careful use of the Singleton Pattern may help here to avoid passing the `MainWindow` object around. – Brett Walker May 04 '15 at 10:38

Alternatives to mock an static method

1 Answers1