Unable to mock a method - junit

Question

I am new to JUNITS and have been trying to use Mockito and PowerMockito for writing some test cases for my code but have been facing an issue.
Class Code:
public class Example implements Callable<Void> {
int startIndex;
int endIndex;
ConnectionPool connPool;
Properties properties;
public Example(int start, int end,
ConnectionPool connPool, Properties properties) {
this.startIndex = start;
this.endIndex = end;
this.connPool= connPool;
this.properties = properties;
}
#Override
public Void call() throws Exception {
long startTime = System.currentTimeMillis();
try {
List<String> listInput = new ArrayList<>();
Service service = new Service(
dbConnPool, properties, startIndex, endIndex);
service.getMethod(listInput);
.
.
.
JUNIT Code:
#RunWith(PowerMockRunner.class)
#PrepareForTest()
public class ExampleTest {
#Mock
private ConnectionPool connectionPool;
#Mock
private Properties properties;
#Mock
private Service service = new Service(
connectionPool, properties, 1, 1);
#Mock
private Connection connection;
#Mock
private Statement statement;
#Mock
private ResultSet resultSet;
#InjectMocks
private Example example = new Example(
1, 1, connectionPool, properties);
#Test
public void testCall() throws Exception {
List<String> listInput= new ArrayList<>();
listInput.add("data1");
when(service.getMethod(listInput)).thenReturn(listInput);
example.call();
}
Question: How to mock Service class and its method, getMethod, call ?
Explanation: The Service class has method getMethod, which is interacting with the DB. So, as I am not able to mock this method, the code goes through and then I have to mock all the objects in the getMethod as connection, resultset etc. else it throws NullPointerException.
Please help me understand what I am doing wrong and if possible provide your guidance on the way I should approach the JUNITS for this kind of method call.

Answer 1

Mockito won't help you to mock an object if you have calling of new Service inside of your method.
Instead you need to use PowerMock.expectNew
Service mockService = PowerMock.createMock(Service.class);
PowerMock.expectNew(Service.class, connectionPool, properties, 1, 1)
.andReturn(mockService);
PowerMock.replay(mockService);
For PowerMockito there is an equivalent:
PowerMockito.whenNew(Service.class)
.withArguments(connectionPool, properties, 1, 1)
.thenReturn(mockService);
Please check this article.