How can i stub Instant object using powermock

Question

Is there a possibility to stub Instant object using Powermock? Powermock has the capability to mock final/static classes/methods.

I wanted something like :

Instant instant = PowerMockito.mock(Instant.now().getClass());
when(instant.getEpochSecond()).thenReturn(76565766587L);

i would need this mocking to be used elsewhere within my service class where i insert into table giving the time of that instant.

Thanks in advance!!

Answer 1

Yes, it is.

My dependencies:

     <dependency>
         <groupId>org.powermock</groupId>
         <artifactId>powermock-module-junit4</artifactId>
         <version>2.0.4</version>
         <scope>test</scope>
     </dependency>
     <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
            <scope>test</scope>
      </dependency>
       <dependency>
            <groupId>org.mockito</groupId>
            <artifactId>mockito-core</artifactId>
            <version>2.28.2</version>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.powermock</groupId>
            <artifactId>powermock-api-mockito2</artifactId>
            <version>2.0.4</version>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.powermock</groupId>
            <artifactId>powermock-core</artifactId>
            <version>2.0.4</version>
            <scope>test</scope>
      </dependency>

And my JUnit:

@RunWith(PowerMockRunner.class)
@PrepareForTest({Instant.class})
public class InstantTest {

    public InstantTest() {
    }

    private Instant mock;

    @Before
    public void setUp() {
        PowerMockito.mockStatic(Instant.class);
        mock = PowerMockito.mock(Instant.class);
        PowerMockito.when(Instant.now()).thenReturn(mock);
    }

    @Test
    public void test() {
        Mockito.doReturn(76565766587L).when(mock).getEpochSecond();
        assertEquals(76565766587L, Instant.now().getEpochSecond());
    }
}

This code works, but IMHO insert into table is about Integration Test, not Unit Test so you need an embedded or testcontainers database and a roundtrip test where you really write data and read it again.