Our sleep is better with longer-scoped tests. Our life is brighter if we don’t rely heavily on fine-grained tests that break whenever we refactor even the smallest detail. I’m talking about tilting the balance towards more integration than unit testing. And for that, let’s look at the testing features offered by the most used Java Framework today. We’ll see how to write fake test implementations, how to mock an unwanted Spring bean, what a Transactional Test is, and if and how to test your web endpoints. Along the way, we’ll also see Flaky tests, and discuss best practices about integration testing – all in an entertaining live coding session. Your takeaways from this talk will be a lot of good practices and techniques directly applicable to your day-to-day project.

1. 113 © VictorRentea.ro
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Integration Testing
with Spring
victorrentea@gmail.com VictorRentea.ro @victorrentea
All code is at https://github.com/victorrentea/unit-testing.git on branch JAX_Mainz

2. Victor Rentea
VictorRentea.ro
Blog, Best Talks, Video Courses, ...
Independent Trainer
for companies and individuals
Founder of
Bucharest Software Craftsmanship Community
Java Champion
❤️ Simple Design, Refactoring, Unit Testing ❤️

3. Technical Training
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More details on VictorRentea.ro
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Clean Code
Refactoring
Unit Testing
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any
lang
@victorrentea
Intense

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files
databases
queues
web services
Integration Tests
Failed Test Tolerance
If your test talks to and it fails,
is it a bug?
Probably not!😏
I hope it's them! 🙏
Tests failed
occasionally
some months after...

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Unit Tests
Integration
failure ➔ maybe a bug
failure ➔ always a bug

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Zero Tolerance for Failed Tests

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🚨 USB device connected to Jenkins

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Let's Test a Search
Search Product
Name:
Supplier: IKEA
Search
...
DEV DB
eg Oracle
H2 in-memory
H2 standalone
DB in Docker
eg Oracle

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Testing...
▪with a Database
▪with external REST calls
▪your REST API
Agenda

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CODE

11. 128 © VictorRentea.ro
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Used to debug test
dependencies
Cleanup After Test
+10-60 wasted seconds
Spring
Don't push it to Jenkins!
@DirtiesContext
or
Manually
Before

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Isolated Repository Tests
@SpringBootTest
@RunWith(SpringRunner.class) // if on JUnit 4
public class TrainingServiceTest {
@Autowired
private TrainingRepo repo;
@Before/@BeforeEach
public void checkEmptyDatabase() {
assertThat(repo.findAll()).isEmpty();
}
@Test
public void getAll() {
...
repo.save(...);
repo.search(...);
....
}
@DirtiesContext(methodMode = AFTER_METHOD)
Recreates the embedded DB
Use For: debugging (time waste)
repo.deleteAll(); ... // others.deleteAll()… // in FK order
@Transactional Run each test in a Transaction,
rolled back after each test.
Best For: Relational DBs
In Large Apps:
Check that the state is clean
Manual Cleanup
Use For: non-transacted resources (eg files, nosql)

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If every test class is @Transactional
Can I still have problems?
YES
Intermediate COMMITs
aka nested transaction
@Transactional(REQUIRES_NEW)

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Inserting Test Data
repo.save()
in @Test
@BeforeEach
@BeforeEach in superclass (inheritance)
@RegisterExtension (composition with JUnit5)
Insert via @Profile
A bean persists data at startup
src/test/resources/data.sql
if you use schema.sql
Incremental Scripts
@Sql

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Composing Fixtures with JUnit5
public class CommonData
implements BeforeEachCallback {
private User user;
public User getUser() {
return user;
}
@Override
public void beforeEach(ExtensionContext context) {
EntityManager em = SpringExtension.getApplicationContext(context)
.getBean(EntityManager.class);
user = new User().setUsername("test");
em.persist(user);
}
}
@RegisterExtension
public CommonData commonData = new CommonData();
@Test
public void noCriteria() {
User user = commonData.getUser();
repo.save(new Post().setCreatedBy(user));
assertThat(repo.findAll()).hasSize(1);
}
in your test class:

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Running SQL Scripts
@Sql("data.sql")
@Sql(script="classpath:cleanup.sql",
phase=BEFORE_TEST_METHOD)
@interface Cleanup {}
before or after @Test
runs in the same transaction
cleanup or initial data insert

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What DB to use in Tests
in-memory H2
(create schema via Hibernate)
Same DB with TestContainers
(create schema via scripts)
Personal Schema on Physical DB
(eg. REGLISS_VICTOR)
Shared Test Schema on Physical DB Legacy 500+ tables schemas
For PL/SQL, custom DB features
For JPA + native standard SQL

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@txn
Feature: Records Search
Background:
Given Supplier "X" exists
Scenario Outline: Product Search
Given One product exists
And That product has name "<productName>"
When The search criteria name is "<searchName>"
Then That product is returned by search: "<returned>"
Examples:
| productName | searchName | returned |
| a | X | false |
| a | a | true |
Gherkin Language
wasted effort
if business never sees it
*
≈ @Before
= Separate transaction / test
.feature

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@Bean
@Mock
Create a Mock
(Mockito)
Define a bean
(Spring)

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@Bean
@Mock
Replaces that bean with a Mockito Mock
(Auto-reset() after each @Test)

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Application Context is Reused
Starting Spring is slow.
Pro Tip:
Maximize Reuse
by test classes with the same:
@ActiveProfiles
@MockBean set
custom properties
locations= .xml
config classes= .class
more

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= +30 sec test run time
Optimizing Spring Tests Speed
1. Tune JVM: -ea -noverify -mx2048m -XX:TieredStopAtLevel=1
6. Limit Auto-Configuration (aka slice tests)
2. Lazy-Load only Tested Beans: spring.main.lazy-initialization=true
3. Disable Web: @SpringBootTest(webEnvironment = NONE)
https://stackoverflow.com/a/49663075 +
https://spring.io/blog/2016/08/30/custom-test-slice-with-spring-boot-1-4
5. Run in parallel
4. Reuse between Test Classes: Sprint Context (#banners) + Dockers + WireMocks
Debugging Test Context reuse: logging.level.org.springframework.test.context.cache=DEBUG
(Least invasive first)

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Reusing Test Context
@SpringBootTest
@Transactional
@ActiveProfiles({"db-mem", "test"})
public abstract class SpringTestBase {
@MockBean
protected FileRepo fileRepoMock;
... all @MockBeans ever needed
}
@ActiveProfiles("db-mem")
public class FeedProcessorWithMockTest
extends SpringTestBase {
@MockBean
when(fileRepoMock).then...
}
nothing requiring
dedicated context

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My Application
SafetyClient
@MockBean
In-memory DB
(H2)
ProductRepo
Remote Sever
Real DB
@Transactional
WireMock
Local Docker
Real DB
.feature
What We've Covered
@DirtiesContext
ProductService
@Transactional

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Unit Tests
Integration
Typically Fast
eg. 100 tests/sec
www . A - color . com
... or Slow
Spring, in-mem DB, Docker
failure ➔ maybe a bug
failure ➔ always a bug
Goal
Run all Honest test after commit
Optimize Test Speed

27. Company Training:
victorrentea@gmail.com
Training for You:
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Thank You!
@victorrentea
Blog, Talks, Curricula:
victorrentea.ro