Mock only selected properties in Spring Environment - spring

Question

I want to be able to use a test properties files and only override a few properties. Having to override every single property will get ugly fast.
This is the code I am using to test my ability to mock properties and use existing properties in a test case
#RunWith(SpringRunner.class)
#SpringBootTest(classes = MyApp.class)
#TestPropertySource(
locations = { "classpath:myapp-test.properties" },
properties = { "test.key = testValue" })
public class EnvironmentMockedPropertiesTest {
#Autowired private Environment env;
// #MockBean private Environment env;
#Test public void testExistingProperty() {
// some.property=someValue
final String keyActual = "some.property";
final String expected = "someValue";
final String actual = env.getProperty(keyActual);
assertEquals(expected, actual);
}
#Test public void testMockedProperty() {
final String keyMocked = "mocked.test.key";
final String expected = "mockedTestValue";
when(env.getProperty(keyMocked)).thenReturn(expected);
final String actual = env.getProperty(keyMocked);
assertEquals(expected, actual);
}
#Test public void testOverriddenProperty() {
final String expected = "testValue";
final String actual = env.getProperty("test.key");
assertEquals(expected, actual);
}
}
What I find is:
#Autowired private Environment env;
testExistingProperty() and testOverriddenProperty() pass
testMockedProperty() fails
#MockBean private Environment env;
testMockedProperty() passes
testExistingProperty() and testOverriddenProperty() fail
Is there a way to achieve what I am aiming for?
Dependencies:
<spring.boot.version>1.4.3.RELEASE</spring.boot.version>
...
<!-- Spring -->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot</artifactId>
<version>${spring.boot.version}</version>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-autoconfigure</artifactId>
<version>${spring.boot.version}</version>
</dependency>
<!-- Starter for testing Spring Boot applications with libraries including JUnit,
Hamcrest and Mockito -->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<version>${spring.boot.version}</version>
</dependency>

Answer 1

Ok i have made this work, you need to use Mockito to accompish what you are looking for:
Maven Dependency
<dependency>
<groupId>org.mockito</groupId>
<artifactId>mockito-core</artifactId>
<version>2.6.4</version>
</dependency>
Test Class Set up
import static org.mockito.Mockito.*;
import static org.springframework.test.util.AopTestUtils.getTargetObject;
#RunWith(SpringRunner.class)
#SpringBootTest(classes = MyApp.class)
#TestPropertySource(
locations = { "classpath:myapp-test.properties" },
properties = { "test.key = testValue" })
public class AnswerTest {
// This will be only for injecting, we will not be using this object in tests.
#Autowired
private Environment env;
// This is the reference that will be used in tests.
private Environment envSpied;
// Map of properties that you intend to mock
private Map<String, String> mockedProperties;
#PostConstruct
public void postConstruct(){
mockedProperties = new HashMap<String, String>();
mockedProperties.put("mocked.test.key_1", "mocked.test.value_1");
mockedProperties.put("mocked.test.key_2", "mocked.test.value_2");
mockedProperties.put("mocked.test.key_3", "mocked.test.value_3");
// We use the Spy feature of mockito which enabled partial mocking
envSpied = Mockito.spy((Environment) getTargetObject(env));
// We mock certain retrieval of certain properties
// based on the logic contained in the implementation of Answer class
doAnswer(new CustomAnswer()).when(envSpied).getProperty(Mockito.anyString());
}
Test case
// Testing for both mocked and real properties in same test method
#Test public void shouldReturnAdequateProperty() {
String mockedValue = envSpied.getProperty("mocked.test.key_3");
String realValue = envSpied.getProperty("test.key");
assertEquals(mockedValue, "mocked.test.value_3");
assertEquals(realValue, "testValue");
}
Implementation of Mockito's Answer interface
// Here we define what should mockito do:
// a) return mocked property if the key is a mock
// b) invoke real method on Environment otherwise
private class CustomAnswer implements Answer<String>{
#Override
public String answer(InvocationOnMock invocationOnMock) throws Throwable {
Object[] arguments = invocationOnMock.getArguments();
String parameterKey = (String) arguments[0];
String mockedValue = mockedProperties.get(parameterKey);
if(mockedValue != null){
return mockedValue;
}
return (String) invocationOnMock.callRealMethod();
}
}
}
Try it out, and let me know if all is clear here.