How to get the full test coverage of the tested method

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I'm writing unit tests for a Spring Boot Service, and I want to get the full coverage of the GET method. Here's my GET method:

public void updateCar(String id, String carModel, Integer HP, Integer year, String designer) {
    Garage garage = garageRepository.findById(id)
            .orElseThrow(() -> new IllegalStateException(
                    "A car with the id " + id + " is not in our Garage."));
    if(carModel != null && carModel.length() > 0 && !Objects.equals(garage.getCarModel(), carModel)) {
        garage.setCarModel(carModel);
    }
    if(HP != null && !Objects.equals(garage.getHP(), HP)) {
        garage.setHP(HP);
    }
    if(year != null && !Objects.equals(garage.getYear(), year)) {
        garage.setYear(year);
    }
    if(designer != null && designer.length() > 0 && !Objects.equals(garage.getDesigner(), designer)) {
        garage.setDesigner(designer);
    }
    garageRepository.save(garage);
}
}

And here is the test method I wrote:

 @Test
    @DisplayName("Update Car Test")
    void testUpdateCar() {

    Garage updatedGarage = new Garage();
    String id = "630ca281f12905d5f5249f08";
    String carModel = "Updated carModel";
    int HP = 480;
    int year = 1964;
    String designer = "Updated designer";

    updatedGarage.setId(id);
    updatedGarage.setCarModel(carModel);
    updatedGarage.setHP(HP);
    updatedGarage.setYear(year);
    updatedGarage.setDesigner(designer);

    when(garageRepository.findById(id))
            .thenReturn(Optional.of(updatedGarage));
    garageService.updateCar(id, carModel, HP, year, designer);

    when(garageRepository.save(updatedGarage))
            .thenReturn(updatedGarage);
    verify(garageRepository).findById(id);
    }

With the test, I only get partial coverage. To be precise, the test didn't include garage.setCarModel(carModel), garage.setHP(HP), garage.setYear(year) nor the garage.setDesigner(designer) from the updateCar method. Can anyone give me a clue or point me in the right direction, on how to get the full coverage?

junit5 spring-boot java
1 Answers

First, understand the paths in the method and then write tests for each path.

There are three main paths and subpaths in the code. To get the full coverage test needs these conditions.

  1. garageRepository.findById(id) ...
  • findById returns a value
  • findById throws Exception
  1. carModel != null && carModel.length() > 0 ...
  • carModel is NOT null.
  • carModel length is NOT 0
  • garage carModel is NOT the same as carModel passed.
  1. if(HP != null && !Objects.equals(garage.getHP(), HP)) ...
  • HP is NOT null
  • HP is NOT the same as HP passed
  1. if(designer != null && designer.length() > 0 ...
  • designer is NOT null.
  • designer length is NOT 0
  • garage designer is NOT same as designer passed.
  1. `garageRepository.save(garage) ...
  • Executes when findById is success.

In the code.

  1. updatedGarage values and values passed to garageService.updateCar must change.
when(garageRepository.findById(id))
            .thenReturn(Optional.of(updatedGarage));
    garageService.updateCar(id, carModel, HP, year, designer);
  1. Add a test for findById to throw an exception.
when(garageRepository.findById(id))
            .thenThrow(NullPointerException.class);
anantha ramu0
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