Issue
I am using JUNIT5, have been trying to fully coverage a piece of code that involves System.getenv(""); I writed a couple classes to replicate what I am experiencing right now and so you can use them to understand me also (minimal reproducible example):
First we have the service I need to get with full coverage (ServiceToTest.class) (it has a CustomContainer object which contains methods that it needs):
@Service
public class ServiceToTest {
private final CustomContainer customContainer;
public ServiceToTest() {
Object configuration = new Object();
String envWord = System.getenv("envword");
this.customContainer = new CustomContainer(configuration, envWord == null ? "default" : envWord);
}
public String getContainerName() {
return customContainer.getContainerName();
}
}
CustomContainer.class:
public class CustomContainer {
@Getter
String containerName;
Object configuration;
public CustomContainer(Object configuration, String containerName) {
this.configuration = configuration;
this.containerName = containerName;
}
}
I have tried using ReflectionTestUtils to set the envWord variable without success... I tried this https://stackoverflow.com/a/496849/12085680, also tried using @SystemStubsExtension https://stackoverflow.com/a/64892484/12085680, and finally I also tried using Spy like in this answer https://stackoverflow.com/a/31029944/12085680
But the problem is that this variable is inside the constructor so this only executes once and I think that it happens before any of this configs I tried before can apply, here is my test class:
@ExtendWith(MockitoExtension.class)
class TestService {
// I have to mock this becase in real project it has methods which I need mocked behavour
private static CustomContainer mockCustomContainer = mock(CustomContainer.class);
// The serviceToTest class in which I use ReflectionTestUtils to use the mock above
// Here is where the constructor gets called and it happens BEFORE (debuged) the setup method
// which is anotated with @BeforeAll
private static ServiceToTest serviceToTest = new ServiceToTest();
@BeforeAll
static void setup() {
// set the field customContainer at serviceToTest class to mockCustomContainer
ReflectionTestUtils.setField(serviceToTest, "customContainer", mockCustomContainer);
}
@Test
void testGetContainerNameNotNull() {
assertNull(serviceToTest.getContainerName());
}
}
I need to write a test in which serviceToTest.getContainerName is not null but the real purpose of this is to have coverage of this sentence envWord == null ? "default" : envWord so it would be a test that is capable of executing the constructor and mocking System.getenv() so that it returns not null...
Right now the coverage looks like this and I can not find a way to make it 100% Any ideas??
EDIT: So after following tgdavies suggestion, the code can be 100% covered, so this is the way:
Interface CustomContainerFactory:
public interface CustomContainerFactory {
CustomContainer create(Object configuration, String name);
}
CustomContainerFactoryImpl:
@Service
public class CustomContainerFactoryImpl implements CustomContainerFactory {
@Override
public CustomContainer create(Object configuration, String name) {
return new CustomContainer(configuration, name);
}
}
EnvironmentAccessor Interface:
public interface EnvironmentAccessor {
String getEnv(String name);
}
EnvironmentAccessorImpl:
@Service
public class EnvironmentAccessorImpl implements EnvironmentAccessor {
@Override
public String getEnv(String name) {
return System.getenv(name);
}
}
Class ServiceToTest after refactoring:
@Service
public class ServiceToTest {
private final CustomContainer customContainer;
public ServiceToTest(EnvironmentAccessor environmentAccessor, CustomContainerFactory customContainerFactory) {
Object configuration = new Object();
String envWord = environmentAccessor.getEnv("anything");
this.customContainer = customContainerFactory.create(configuration, envWord == null ? "default" : envWord);
}
public String getContainerName() {
return customContainer.getContainerName();
}
}
Finally the test case after refactoring (here is were I think it can be improved maybe?):
@ExtendWith(MockitoExtension.class)
class TestService {
private static CustomContainer mockCustomContainer = mock(CustomContainer.class);
private static CustomContainerFactory customContainerFactoryMock = mock(CustomContainerFactoryImpl.class);
private static EnvironmentAccessor environmentAccessorMock = mock(EnvironmentAccessorImpl.class);
private static ServiceToTest serviceToTest;
@BeforeAll
static void setup() {
when(environmentAccessorMock.getEnv(anyString())).thenReturn("hi");
serviceToTest = new ServiceToTest(environmentAccessorMock, customContainerFactoryMock);
ReflectionTestUtils.setField(serviceToTest, "customContainer", mockCustomContainer);
when(serviceToTest.getContainerName()).thenReturn("hi");
}
@Test
void testGetContainerNameNotNull() {
assertNotNull(serviceToTest.getContainerName());
}
@Test
void coverNullReturnFromGetEnv() {
when(environmentAccessorMock.getEnv(anyString())).thenReturn(null);
assertAll(() -> new ServiceToTest(environmentAccessorMock, customContainerFactoryMock));
}
}
Now the coverage is 100%:
Solution
Refactor your code to make it testable, by moving object creation and static method calls to components, which you can mock in your tests:
interface ContainerFactory {
CustomContainer create(Object configuration, String name);
}
interface EnvironmentAccessor {
String getEnv(String name);
}
@Service
public class ServiceToTest {
private final CustomContainer customContainer;
public ServiceToTest(ContainerFactory containerFactory, EnvironmentAccessor environmentAccessor) {
Object configuration = new Object();
String envWord = environmentAccessor.getEnv("envword");
this.customContainer = containerFactory.create(configuration, envWord == null ? "default" : envWord);
}
public String getContainerName() {
return customContainer.getContainerName();
}
}
Answered By - tgdavies
Answer Checked By - David Goodson (JavaFixing Volunteer)
