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Why does autowired repository result in a NullPointerException in Junit4 context?

I'm new to Java development so sorry in advance if I'm not using the appropriate terms.
Whenever I run a test on a class that needs to save something in my database, I face a NullPointerException on the Autowired repository.
I use Junit4, here are code snippets :
application-test.properties
spring.datasource.url=jdbc:tc:mysql:8.0.29://localhost:3306/MYSERVICE
MyService.java
#Component
class MyService {
#Autowired MyRepository myRepository;
public void mainFunction() {
myRepository.saveSomething();
}
}
MyRepository.java
#Repository
public interface MyRepository extends JpaRepository<T, Long> {
void saveSomething();
}
MyServiceTest.java
public class myServiceTest extends TestConfiguration {
#Rule
public MySQLContainer mysql = new MySQLContainer();
#InjectMocks MyService myService;
#Test
public void mainFunctionTest() {
myService.mainFunction()
}
}
MyServiceTestApplication.java
#SpringBootApplication(exclude = {
DataSourceAutoConfiguration.class
})
public class MyServiceTestApplication{
}
TestConfiguration.java
#RunWith(SpringRunner.class)
#SpringBootTest(classes = MyServiceTestApplication.class)
#ActiveProfiles("test")
public abstract class TestConfiguration {
}
When I run the test in debug mode, I can see that myRepository is null
Any help would be highly appreciated
Thanks :)
Edit 01/08/2022 : Add #Component on MyService
Edit 01/08/2022 (2) : Add MyServiceTestApplication.java and TestConfiguration.java

It seems, you forgot to annotate the class MyService with #Service.
With this annotation being made at that class, the Spring framework will recognize it:
This annotation serves as a specialization of #Component, allowing for
implementation classes to be autodetected through classpath scanning.
Given that the rest of the configuration is working, the #Autowired dependency injection mechanism will hereby provide you with an instance of the #Repository you requested, at runtime, here your test setup.

How do I put TestConfiguration in an abstract class?

I have some Spring tests that all define the same test configuration:
#TestConfiguration
public static class TestConfig {
#Bean
public EmployeeClient employeeClient(MockMvc mockMvc) {
return new EmployeeClient(mockMvc);
}
}
To reduce replication I put that code into an abstract class and had each test extend that abstract class. However, this threw Spring unresolved dependencies - it couldn't resolve EmployeeClient.
How can I make this work?

One of the ways is to make your Test class use multiple configuration files.
#Configuration
class CommonBeans {
}
#Configuration
class SpecificBeans {
}
#ContextConfiguration(classes = {CommonBeans.class, SpecificBeans.class})
public class MyAppTest {
------
}
In your test package if you are creating a configuration using #TestConfiguration instead of #Configuration then you have to use #Import annotation to make use of that.
#TestConfiguration
public class TestBeans {
}
#Import(TestBeans.class)
public class MyAppTest {
------
}

How to add a bean in SpringBootTest

The question seems extremely simple, but strangely enough I didn't find a solution.
My question is about adding/declaring a bean in a SpringBootTest, not overriding one, nor mocking one using mockito.
Here is what I got when trying the simplest implementation of my real need (but it doesn't work):
Some service, bean, and config:
#Value // lombok
public class MyService {
private String name;
}
#Value // lombok
public class MyClass {
private MyService monitoring;
}
#Configuration
public class SomeSpringConfig {
#Bean
public MyClass makeMyClass(MyService monitoring){
return new MyClass(monitoring);
}
}
The test:
#RunWith(SpringRunner.class)
#SpringBootTest(classes = { SomeSpringConfig.class })
public class SomeSpringConfigTest {
private String testValue = "testServiceName";
// this bean is not used
#Bean
public MyService monitoringService(){ return new MyService(testValue); }
// thus this bean cannot be constructed using SomeSpringConfig
#Autowired
public MyClass myClass;
#Test
public void theTest(){
assert(myClass.getMonitoring().getName() == testValue);
}
}
Now, if I replace the #Bean public MyService monitoring(){ ... } by #MockBean public MyService monitoring;, it works. I find it strange that I can easily mock a bean, but not simply provide it.
=> So how should I add a bean of my own for one test?
Edit:
I think ThreeDots's answer (create a config test class) is the general recommendation.
However, Danylo's answer (use #ContextConfiguration) fit better to what I asked, i.e. add #Bean directly in the test class.

Spring Test needs to know what configuration you are using (and hence where to scan for beans that it loads). To achieve what you want you have more options, the most basic ones are these two:
Create configuration class outside the test class that includes your bean
#Configuration
public class TestConfig {
#Bean
public MyService monitoringService() {
return new MyService();
}
}
and then add it to to test as configuration class #SpringBootTest(classes = { SomeSpringConfig.class, TestConfig.class })
or
If you only need to use this configuration in this particular test, you can define it in static inner class
public class SomeSpringConfigTest {
#Configuration
static class ContextConfiguration {
#Bean
public MyService monitoringService() {
return new MyService();
}
}
}
this will be automatically recognized and loaded by spring boot test

Simply add the config as
#ContextHierarchy({
#ContextConfiguration(classes = SomeSpringConfig.class)
})

What i am using in this cases is #Import:
#DataJpaTest(showSql = false)
//tests against the real data source defined in properties
#AutoConfigureTestDatabase(replace = AutoConfigureTestDatabase.Replace.NONE)
#Import(value = {PersistenceConfig.class, CustomDateTimeProvider.class})
class MessageRepositoryTest extends PostgresBaseTest {
....
Here i am using a pre configured "test slice".
In this case a need to add my JpaAuditingConfig.
But why not just adding the other beans as you did with your SomeSpringConfig.class ?:
#RunWith(SpringRunner.class)
#SpringBootTest(classes = { SomeSpringConfig.class, OtherBean.class })
public class SomeSpringConfigTest {
...
Everything listed in test will be injectable directly, all not declared must be added as mocks.

Overriding spring #Configuration in an integration test

I have a spring boot configuration class like this:
#Configuration
public class ClockConfiguration {
#Bean
public Clock getSystemClock() {
return Clock.systemUTC();
}
}
and I have some integration tests like this:
#SpringBootTest(classes = MyApplication.class, webEnvironment = WebEnvironment.RANDOM_PORT)
public abstract class AbstractIntegrationTest {
}
and tests like this:
public class MiscTests extends AbstractIntegrationTest{
#Test
public void CreateSomethingThatOnlyWorksInThe Morning_ExpectCorrectResponse() {
}
I want to be able to offset the clock bean to run some tests at different times on the day. How do I do this?
NOTE: I see several stack overflow answers similar to this, but I can't get them to work.
Based on other responses, it appears the solution should be something like:
#SpringBootTest(classes = MyApplication.class, webEnvironment = WebEnvironment.RANDOM_PORT)
public abstract class AbstractIntegrationTest {
#Configuration
class MyTestConfiguration {
#Bean
public Clock getSystemClock() {
Clock realClock = Clock.systemDefaultZone();
return Clock.offset(realClock, Duration.ofHours(9));
}
}
}
But nothing happens there. Do I need to #Import something? do I need to #Autowired something?
Thanks!

As you are using Spring Boot you can take advantage of the #MockBean annotation:
#SpringBootTest(classes = MyApplication.class, webEnvironment = WebEnvironment.RANDOM_PORT)
public abstract class AbstractIntegrationTest {
#MockBean
private Clock clockMock;
}
Then you can stub public methods of that bean an each of the tests accordingly and uniquely:
#Test
public void CreateSomethingThatOnlyWorksInThe Morning_ExpectCorrectResponse() {
when(clockMock.getTime()).thenReturn(..);
}
As per javadoc of #MockBean:
Any existing single bean of the same type defined in the context will
be replaced by the mock.

it is the #TestConfiguration annotation that you need https://docs.spring.io/spring-boot/docs/current/api/org/springframework/boot/test/context/TestConfiguration.html
#RunWith(SpringRunner.class)
public class ClockServiceImplIntegrationTest {
#TestConfiguration
static class TestOverridingClockServiceConfiguration {
#Bean
public ClockService clockService() {
return new ClockServiceImpl();
}
}
#Autowired
private ClockService clockService;
#MockBean
private ClockRepository clockRepository;
// write test cases here
}
In the case you have existing configuration you c

Use different Spring test context configuration for different test methods

We have a Spring based JUnit test class which is utilizing an inner test context configuration class
#RunWith(SpringJUnit4ClassRunner.class)
#ContextConfiguration(classes = ServiceTest.Config.class)
public class ServiceTest {
#Test
public void someTest() {
...
#Configuration
#PropertySource(value = { "classpath:application.properties" })
#ComponentScan({ "..." })
public static class Config {
...
New functionalities have been recently introduced to the Service class, for which the concerned tests should be added to ServiceTest. However these would also require a different test context configuration class to be created (the internals of the existing Config class are fairly complex and change it to serve both old and new tests seems to be be extremely difficult if possible at all)
Is there a way to achieve that certain test methods in one test class would use one config class and other methods would use another? #ContextConfiguration seems to be applicable only on class level, so solution could be to create another test class for the new tests which would utilize its own context configuration class; but it would mean that the same Service class is being covered via two different test classes

With Aaron's suggestion of manually building the context I couldn't find any good examples so after spending some time getting it working I thought I'd post a simple version of the code I used in case it helps anyone else:
class MyTest {
#Autowired
private SomeService service;
#Autowired
private ConfigurableApplicationContext applicationContext;
public void init(Class<?> testClass) throws Exception {
TestContextManager testContextManager = new TestContextManager(testClass);
testContextManager.prepareTestInstance(this);
}
#After
public void tearDown() throws Exception {
applicationContext.close();
}
#Test
public void test1() throws Exception {
init(ConfigATest.class);
service.doSomething();
// assert something
}
#Test
public void test2() throws Exception {
init(ConfigBTest.class);
service.doSomething();
// assert something
}
#ContextConfiguration(classes = {
ConfigATest.ConfigA.class
})
static class ConfigATest {
static class ConfigA {
#Bean
public SomeService someService() {
return new SomeService(new A());
}
}
}
#ContextConfiguration(classes = {
ConfigBTest.ConfigB.class
})
static class ConfigBTest {
static class ConfigB {
#Bean
public SomeService someService() {
return new SomeService(new B());
}
}
}
}

I use these approaches when I'm have to solve this:
Manually build the context in a setup method instead of using annotations.
Move the common test code to a base class and extend it. That allows me to run the tests with different spring contexts.
A mix of the two above. The base class then contains methods to build spring contexts from fragments (which the extensions can override). That also allows me to override test cases which don't make sense or do extra pre/post work in some tests.
Keep in mind that annotations only solve generic cases. You'll have to replicate some or all of their work when you leave the common ground.