How to test switch case in Junit using Mockito

I am able to test the code but code coverage does not cover second switch case.

Please refer the below code.

 { @PersistenceContext
	EntityManager manager;

	@Autowired
	TurbineRepository turbineRepository;

	@Autowired
	WorkRepository workRepository;

	public Dropdown getDropdown(String type) {
		Dropdown dropdownDTO = new Dropdown();
		switch(type) {
		case "turbine":
			List<String> turbinesList = turbineRepository.listOfTurbines();
			dropdownDTO.setTurbinesList(turbinesList);
			break;
		case "wocreate":
			List<String> turbineList = turbineRepository.listOfTurbines();
			dropdownDTO.setTurbinesList(turbineList);
			List<ParamsProjection> params = workRepository.findBy();
			Map<String, List<ParamsProjection>> result = params.stream()
					.collect(Collectors.groupingBy(ParamsProjection::getType));
			dropdownDTO.setParams(result);
		default:
		}
		return dropdownDTO;

	}

Below is my test code.

{
    @InjectMocks
	private Services service;
	
	@Mock
	private WorkRepository workRepo;
	
	@Mock
	private TurbineRepository turbineRepo;
	
	@Mock
	private ParamsProjection paramProject1;
	
	@Test 
	public void getDropDown() {
		
		Dropdown dto = new Dropdown();
		List<String> turbineList = new ArrayList<String>();
		String type = "turbine";
		switch(type) {
		case "turbine" :
		Mockito.when(turbineRepo.listOfTurbines()).thenReturn(turbineList);
		dto.setTurbinesList(turbineList);
		assertNotNull(dto);
		break;
		
		case "wocreate": 
		DropdownDTO dto2 = new DropdownDTO();
		Mockito.when(turbineRepo.listOfTurbines()).thenReturn(turbineList);
		dto2.setTurbinesList(turbineList);
		List<ParamsProjection> param = new ArrayList<ParamsProjection>();
		Mockito.when(workRepo.findBy()).thenReturn(param);
		
		Map<String, List<ParamsProjection>> result = param.stream()
				.collect(Collectors.groupingBy(ParamsProjection::getType));
		
		dto2.setParams(result);
		assertNotNull(dto2);
		break;
}
        assertNotNull(service.getDropdown("turbine"));
}

As I have declared a string variable with value for testing , I am not able to cover the second switch statement.
I have tried if-else case but same problem occurs.
Is there any other way we can do this?

Your type is always "turbine", so just that case is tested. It would make sense to have two different tests, one for each type:

@Test 
public void getDropDownTurbine() {
    
    Dropdown dto = new Dropdown();
    List<String> turbineList = new ArrayList<String>();
    String type = "turbine";
    Mockito.when(turbineRepo.listOfTurbines()).thenReturn(turbineList);
    dto.setTurbinesList(turbineList);
    assertNotNull(dto);
    assertNotNull(service.getDropdown("turbine"));
} 


@Test 
public void getDropDown() {
    
    List<String> turbineList = new ArrayList<String>();
    String type = "wocreate";
    DropdownDTO dto2 = new DropdownDTO();
    Mockito.when(turbineRepo.listOfTurbines()).thenReturn(turbineList);
    dto2.setTurbinesList(turbineList);
    List<ParamsProjection> param = new ArrayList<ParamsProjection>();
    Mockito.when(workRepo.findBy()).thenReturn(param);
    
    Map<String, List<ParamsProjection>> result = param.stream()
            .collect(Collectors.groupingBy(ParamsProjection::getType));
    
    dto2.setParams(result);
    assertNotNull(dto2);

    assertNotNull(service.getDropdown("wocreate"));
} 

Instead of writing two different test cases you can simply use single parameterized test in which you can set different String value for each iteration.

`@ParameterizedTest
 @ValueSource(strings = {"value1", "value2"})
 void testMethod(String str) {
        //testLogic
 }`