Junit & Mockito [Spring Basics-4]

JUnit

• JUnit is a unit testing framework for Java and can be used for automation testing in CI/CD pipeline.
• Junit methods - assertTrue(condn),assertFalse(condn),assertEquals(expected,actual),assertNull(),assertArrayEquals(expected,actual)
• Junit annotations - @Test,@Before(runs before every test),@After,@BeforeClass,@AfterClass.

Example of JUnit

sampleTest.java

class sampleTest {
    @Test
    void test_for_both_positive() {
        sample s = new sample(); // we wanna test sample class's add method
        assertEquals(2,s.add(1,1));
    }
}

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Mockito

• How to test a piece of code without implementing and testing its dependencies.
• Without mockito we will have to create a stub, but problem is for different cases we have to create different stubs hence Mockito is used.
• Annotations provided are @RunWith(MockitoJUnitRunner.class), @Mock, @InjectMocks
• Before looking at example, lets take a look at mocking a class's function without annotations. Suppose class A's AFunc is dependant on B(It has a function BFunc). Now instead of creating a stub(fake function within B) we can mock it using Mockito.

@Test
void Test(){
    B bmock = mock(B.class);
    when(bmock.BFunc()).thenReturn(new String("Hello")); //when this function is called return this value
    A a = new A(bmock); // injecting using constructor injection
    String result = a.AFunc();
    assertEquals(-2,res);
}

Example of Mockito -

We have Data which is dependent on DataService, so we mock DataService.

Data.java

public class Data {
    public DataService dataService;

    public Data(DataService dataService){
        this.dataService=dataService;
    }

    public int findGreatest() {
        int[] data = dataService.retrieveAllData();
        int greatest = Integer.MIN_VALUE;

        for(int i: data) 
            greatest = Math.max(greatest, i);

        return greatest;
    }
}

DataService.java

public interface DataService {
    int[] retrieveAllData();
}

testData.java

@RunWith(MockitoJUnitRunner.class)
class test_Data {
    @Mock
    DataService dataservicemock;

    @InjectMocks
    Data ob;

    @Test
    void test1() {
        when(dataservicemock.retrieveAllData()).thenReturn(new int[] {20,40,2,19});
        int res = ob.findGreatest();
        assertEquals(40,res);
    }
}