Java Testing Notes
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suppress() works best for void methods or constructors, but what if need to return something. For that we have stub().
// Example Source Class
public class ExampleClass extends CustomLibClass {
public int someMethod() {
final int valueFromSuper = super.someMethodThatOnlyWorksOnRumtime();
return valueFromSuper * 2;
Here, we have a method with that return something, and to test our method we need get a fixed value from CustomLibClass.someMethodThatOnlyWorksOnRumtime(). To achive that, we can use stub().
public class ExampleClassTest {
private ExampleClass classUnderTest;
public void setUp() throws Exception {
// Create constructor of ExampleClass
classUnderTest = new ExampleClass();
public void someMethod_shouldReturnFour_whenCustomLibSomeMethodThatOnlyWorksOnRumtimeReturnTwo() throws NoSuchMethodException {
// Given
// When
final int actualResult = classUnderTest.someMethod();
// Then
// As we stubbed someMethodThatOnlyWorksOnRumtime() to return 2, our result will be 2 * 2 = 4
Assert.assertEquals(4, actualResult);
Note: keep in mind, if you need to manipulate behavior (byte code) of any class, as we are doing in case of stub method, we need to add ExampleClass.class in @PrepareForTest.