Why Spring #Service methods appear with 0% code coverage in JaCoCo? - spring

Question

These libraries are loaded:
JUnit 5.3.2
JaCoCo 0.8.2
Mockito 2.10.0
Only element "static {...}" appears with 100% coverage. All the rest is at 0%:
The unit test class has annotations #ExtendWith(SpringExtension.class) and #AutoConfigureMockMvc. The service is injected with #Mock.
doReturn(actual).when(service).get(param);
when(service.get(param)).thenReturn(actual);
expected = service.get(param);
verify(service, times(1)).get(param);
assertEquals(expected, actual);
assertEquals(actual, expected);
My ServiceImpl class is red when I click any method. It extends an abstract class. Jackson's ObjectMapper is red, and also the entire lines within the methods. For example:
public CustomReturnObject get(final CustomParamObject paramObject) {
try {
return retryTemplate.execute(status -> {
String json = repository.get(paramObject);
CustomReturnObject returnObject = json2CustomObject(json, paramObject);
if (returnObject == null) {
returnObject = new CustomReturnObject();
returnObject.setId(paramObject.getId());
}
return returnObject;
});
} catch (Exception ex) {
log.error(ex.getMessage(), ex);
return null;
}
}

Answer 1

Similarly to https://stackoverflow.com/a/46614216/244993 let's put aside Spring, because there is IMO clearly something wrong with your expectations/understanding about core thing here - mocking.
By
doReturn(actual).when(service).get(param);
expected = service.get(param);
verify(service, times(1)).get(param);
assertEquals(expected, actual);
you are not testing get method, you are testing something that always returns actual, no matter what is actually written in get, because in this case it is not executed.
Here is complete example as a proof:
src/main/java/hello/GreetingService.java:
package hello;
class GreetingService {
Object get(Object param) {
throw new UnsupportedOperationException();
}
}
src/test/java/hello/GreetingServiceTest.java:
package hello;
import org.junit.jupiter.api.Test;
import org.junit.jupiter.api.extension.ExtendWith;
import org.mockito.Mock;
import org.mockito.Mockito;
import org.mockito.junit.jupiter.MockitoExtension;
import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.mockito.Mockito.doReturn;
import static org.mockito.Mockito.verify;
#ExtendWith(MockitoExtension.class)
public class GreetingServiceTest {
#Mock
public GreetingService service;
#Test
void test() {
Object param = new Object();
Object actual = new Object();
doReturn(actual).when(service).get(param);
Object expected = service.get(param);
verify(service, Mockito.times(1)).get(param);
assertEquals(expected, actual);
}
}
build.gradle :
apply plugin: 'java'
sourceCompatibility = 1.8
targetCompatibility = 1.8
repositories {
mavenCentral()
}
dependencies {
testCompile 'org.mockito:mockito-junit-jupiter:2.23.4'
}
Real method get throws UnsupportedOperationException, however above test succeeds, so real method was not executed. As another way to proof that get not executed: put a breakpoint into it and execute test in debug mode from IDE - breakpoint won't be reached.
Coverage shows what was really executed and hence absolutely correct that it is zero for methods that are not executed.