Mockito - Set default return string value for all mocked methods

Question

I have a class that has over 20 methods that return string values. These strings are not relevant for my test, but it's pretty time consuming to set a when->thenReturn case for each of the functions, specially because there are several of these classes.

Is there a way to tell mockito to default empty string instead of null, or any string value that I wish for that matter?

Answer 1

I created a class to perform this on your project whenever needed, simply init the mock (usually in @Before function)

myClassMock = mock(MyClass::class.java, NonNullStringAnswer())

NonNullStringAnswer.kt

/** Used to return a non-null string for class mocks.
 *
 * When the method called in the Mock will return a String, it will return the name of the
 * method instead of null.
 *
 * For all other methods the default mocking value will be returned.
 * 
 * If you want to mock additional methods, it is recommended to use doReturn().when instead on
 * when().thenReturn
 *
 * Example of usage:
 *
 * myClassMock = mock(MyClass::class.java, NonNullStringAnswer())
 *
 **/
class NonNullStringAnswer : Answer<Any> {
    @Throws(Throwable::class)
    override fun answer(invocation: InvocationOnMock): Any {
        return if (invocation.method.returnType == String::class.java) {
            invocation.toString()
        } else {
            Mockito.RETURNS_DEFAULTS.answer(invocation)
        }
    }
}