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SpringBoot, JPA and Hibernate Unit-Test for Entities layer

I'm implementing a project using SpringBoot, JPA and Hibernate.
I implemented the DB entities layer with JPA repository.
I'm interested to understand the best practice to write unit-tests for this layer.
Point number one: for this layer, from your point of view, it's necessary to use an integrated DB or it' necessary to mock using, for example, Mockito?
My idea, for this layer, it's, for example, to test the entity structure: check fields validation for example, insert and retrieve some data. In this way, I think I could cover the tests for this entire data-layer.
I'm trying to understand these best practices and, in the mean time, I tried to write a first example of the test:
#ActiveProfiles("test")
#DisplayName("Test Item JPA Entity")
#DataJpaTest
#AutoConfigureTestDatabase( replace = AutoConfigureTestDatabase.Replace.NONE )
public class ItemEntityTest {
#Autowired
MyEntityRepository repo;
#Test
#Transactional
public void testEntityCreation() {
Entity e = new Entity();
e.setMyField1("A");
e.setMyField1("A");
//e.setMandatoryField("C")
repo.save(e);
}
}
Unfortunately, In this case, I notiest that the fields validation is not applied (#NotNull or #NotEmpty, or #Column(nullable=false), etc ... If I try to save the entity into my application the validation works fine... the exceptions are raised). Why?
Also some "automatic fields" (for example creation time and last modification time) are not filled.
Is this the correct path? Ho to test my entities definition?

As mentioned in that answer, the problem is that with #DataJpaTest spring will use TestEntityManager and the transactional annotation will override the default auto commit and rollback behaviour by spring boot.
So your test method will pass and assuming the hibernate is the ORM being used here, when the flushing will take place finally, hibernate's pre-insert event will fire and validations will be applied, but your test case will pass till then so it will produce false positive (as the terms used in spring docs)
Solution: You would need to inject entity manager in your test and flush manually it so that hibernate pre-insert event triggers before your test completes.
#ActiveProfiles("test")
#DisplayName("Test Item JPA Entity")
#DataJpaTest
#AutoConfigureTestDatabase( replace = AutoConfigureTestDatabase.Replace.NONE )
public class ItemEntityTest {
#Autowired
MyEntityRepository repo;
#Autowired
private TestEntityManager em;
#Test
#Transactional
public void testEntityCreation() {
Entity e = new Entity();
e.setMyField1("A");
e.setMyField1("A");
//e.setMandatoryField("C")
repo.save(e);
em.flush();
}
}
This must trigger your validations on the entity applied, this is documented in spring framework docs.
Please notice that the documentation is about spring framework and uses session factory, but the concept is same
You may check the spring boot docs as well, which points to the spring framework docs for this behaviour.

Junit Spring avoid to load twice application context datasource

I have this configuration classes:
#ComponentScan(
basePackages = {
"mypackage.controller",
"mypackage.service",
"mypackage.repository"
}
)
#TestPropertySource(locations="classpath:configuration.properties")
#Import({
H2Configuration.class
})
public class TestConfiguration {
}
#Configuration
public class H2Configuration {
#Bean
public DataSource dataSource() throws SQLException {
EmbeddedDatabaseBuilder builder = new EmbeddedDatabaseBuilder();
EmbeddedDatabase db = builder
.setType(EmbeddedDatabaseType.H2)
.addScript("h2/create.sql")
.addScript("h2/insert.sql")
.build();
db.getConnection().setAutoCommit(false);
return db;
}
}
And I have this two class tests:
#RunWith(SpringJUnit4ClassRunner.class)
#ContextConfiguration(loader=AnnotationConfigContextLoader.class, classes = { TestConfiguration.class })
public class FirstRepositoryTest {
#Autowired
MyFirstRepositoryImpl repository;
#Before
public void initTest() {
}
#Test(expected = NullPointerException.class)
public void testNullRecords() {
repository.foo(null, null);
}
}
#RunWith(SpringJUnit4ClassRunner.class)
#ContextConfiguration(loader=AnnotationConfigContextLoader.class, classes = { TestConfiguration.class })
public class SecondRepositoryTest {
#Autowired
MySecondRepositoryImpl repository;
#Before
public void initTest() {
}
#Test(expected = NullPointerException.class)
public void testSomethingNullRecords() {
repository.something(null, null);
}
}
If I run junit test once for each class, all goes well.
In clean install phase tests fails because the application context is initialized twice.
For example it try to create the h2 tables twice and do the insert.sql script twice.
What I have to do for initialize the h2 database and so application context only once?
Thanks

I think you could start looking at the Spring documentation about Integration Testing.
It can also be a good practice to use transactional tests for integration tests (#Transactional), which rollback at the end of each test : see Transaction Management.
To avoid the cost of recreating the ApplicationContext for each test class, the cache may be used as explained here : Context Caching.
For integration testing with Embedded Database, you can also find documentation : Testing Data Access Logic with an Embedded Database.
A note from the previous link, matching your use case :
However, if you wish to create an embedded database that is shared
within a test suite, consider using the Spring TestContext Framework
and configuring the embedded database as a bean in the Spring
ApplicationContext as described in Creating an Embedded Database by
Using Spring XML and Creating an Embedded Database Programmatically.
I hope you will find some useful references.

Another good tip I found from Spring Boot documentation from Embedded Database Support :
They say :
If you are using this feature in your tests, you may notice that the
same database is reused by your whole test suite regardless of the
number of application contexts that you use. If you want to make sure
that each context has a separate embedded database, you should set
spring.datasource.generate-unique-name to true.
So to make each EmbeddedDatabase unique, you may try to create them with :
EmbeddedDatabase db = new EmbeddedDatabaseBuilder()
.generateUniqueName(true)
...
.build();

In unit testing you must garantee that every test is repeatible hance context independent. Due to this is not good idea to load the context only once. Is better to reset after the execution. For this you can use #DirtiesContext(classMode = ClassMode.AFTER_CLASS) in your test classes
So you will force your context to restart when the next junit class is launched

So the reason that this is failing is that the database (H2) is resident in memory when you run the tests as part of clean/install. The create/insert scripts have already executed after the first test is run. Any subsequent test execution after this point will result in a re-execution of the same script(s) and the error will occur.
Update your create script with a DROP TABLE IF EXISTS <table name>;. This will ensure that the table is dropped then recreated.
NOTE: I'm not sure why you've specified AnnotationConfigContextLoader explicitly. I think, without that, the runner SpringJUnit4ClassRunner will cache contexts that have not been changed. I don't know specifically if that is the case here though.

Prevent Spring bean re-initialization for each JUnit test

I have integration tests based on JUnit that access DB. We also use Liquibase Spring bean to init database.
If I try running multiple tests in parallel each of them tries to initialize DB using Liquibase causing locks and eventually failures since only one instance of Liquibase can modify DB at a time.
The tests are configured as follows:
#RunWith(SpringJUnit4ClassRunner.class)
#Transactional
#WebAppConfiguration
#Sql({"/schema/insert-test-data.sql"})
How can I configure DB initialization (schema and data) that it will be done only once and not for each test?

This is just idea not testet, but if you are not executing scripts in parallel what about using ScriptUtils or ResourceDatabasePopulator iside #Before method with some switch.
#Before
public void init(){
if (wasInitialized)
return;
new ResourceDatabasePopulator(new ClassPathResource("path/to/sql.sql")).execute(dataSource);
wasInitialized = true;
}

Spring/DBUnit dont rollback transaction until the end of test

We are using dbunit with spring boot and H2 database for local unit/integration testing. In the test we are using TransactionDbUnitTestExecutionListener and #Transactional annotations so that the transaction during the test does not rollback until the end.
However, I observed that if in the test I call a function with Propogation.REQUIRES_NEW, the rollback occurs immediately after the function returns and then test fails because it cannot find the data.
Here is the example code
#Test
#Transactional
#DatabaseSetup("/Uploads.xml")
#Rollback(value = false)
fun testStampSidekiqJobId() {
uploadEntity = uploadService.stampSidekiqJobId(uploadEntity, "fakeJobId")
// test values
}
// here is the called function
#Transactional(propagation = Propagation.REQUIRES_NEW)
open fun stampSidekiqJobId(uploadEntity:UploadEntity, encodeJobId:String): UploadEntity {
I have tried with and without Rollback annotation. Please note that the class hosting this unit test has DependencyInjectionTestExecutionListener, TransactionDbUnitTestExecutionListener annotations.

Testing Hibernate DAO using Junit

I am using a combination of Spring and Hibernate in my project and would like to test the DAO methods like Save and Delete methods.
daoFoundation is a wrapper class created over hibernateSession.
#Override
public String createSubject(Subject subject) {
String subjectId = (String) daoFoundation.save(subject);
return subjectId;
}
This is what I wrote in my JUnit Runs with SpringJunit4ClassRunner
I created the subject object in my SetupMethod.
#Test
public void createSubjectTest(){
subjectDao.createSubject(subject);
assertNotNull(hassSubjectSelection.getId());
}
Is this sufficient or do I need to write anything additional in my test class?

The easiest way is to import your Spring application context, autowire in the DAO's you want to test and then mark either your test methods or the entire class as #Transactional. This will create a Hibernate session, run your test and then automatically roll back the transaction so you don't effect your database state with your tests.
Have a look at how to run unit tests with Spring here. You can get Spring to create your entire application context using the #ContextConfiguration annotation. So if you create your database using an XML file called database-servlet.xml then you would annotate
#ContextConfiguration(locations={"classpath:/database-servlet.xml"})
public class Test()
You can use the annotation #RunWith(SpringJUnit4ClassRunner.class) to use functionality of the Spring TestContext Framework with your unit tests. This allows you to do things like declare expected exceptions that should be thrown, run timed tests, repeat test runs X times and a bunch of other cool stuff.
Basically to get this working, your test class should look similar to the following:
#RunWith(SpringJUnit4ClassRunner.class)
#ContextConfiguration(locations={YOUR APP CONTEXT FILES HERE AS A COMMA SEPARATED LIST})
public class Test(){
#Autowired
private YourDAO yourDAO;
#Test
#Transactional
public void testSave(){
//Test save method here. Any database changes made here will be
//automatically rolled back when the test finishes.
}
Let me know if that works or not.

The best way to test your dao layer is to use the spring jdbctemplate to write data to your database the test your get and delete methods. Then in the #after delete the records you wrote. Then use hibernate to write to your database and use jdbctemplate to read them back. Then delete your test rows. Anything less and all you are really doing is testing hibernate's caching.