This document provides an overview of integration testing strategies and techniques. It discusses the differences between unit tests and integration tests, including that integration tests involve multiple layers and dependencies like databases, files, and web services, making them slower and more fragile. It also covers best practices for integration tests such as using an in-memory database, WireMock for stubbing external services, transaction management, and strategies for cleaning up after tests.

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Integration Testing
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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 not! 🙏
Tests failed
occasionally
some months after...

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Unit Tests
Integration
Deep
many layers
Fragile
DB, REST APIs, files
Fast
eg. 100 tests/sec
Slow
app startup,
network
... or Slow
in-mem DB, Spring,
Docker
failure ➔ maybe a bug
failure ➔ bug
Tiny
fine-grained
extensive mocks

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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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CODE

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@ActiveProfile("db-mem")
Toggle @Component, @Bean or @Configuration
Overrides properties with application-db-mem.properties

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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(entity);
var results = repo.search(...);
assertEquals(...);
}
@DirtiesContext(methodMode = DirtiesContext.MethodMode.AFTER_METHOD)
Safest but wastes time
Use For: debugging
repo.deleteAll(); ... // others.deleteAll()… // in FK order
@Transactional Run each test in a Transaction,
rolled back after each test.
Use 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
in @BeforeEach
in superclass
in @RegisterExtension (JUnit5)
Insert via @Profile
A Spring bean persisting data at app startup
src/test/resources/data.sql
(auto-inserted after src/test/resources/schema.sql creation)
@Sql
CascadeType.PERSIST
helps A LOT !

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Running SQL Scripts
@Sql
@Sql("data.sql")
@Sql({"schema.sql", "data.sql"})
On method or class
@SqlMergeMode
TestClass.testMethod.sql
before or after @Test
in the same transaction

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What DB to use in Tests
in-memory H2
(create schema via Hibernate)
Same DB in Local Docker
(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, native features
For JPA + native standard SQL

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Invest hours, days, weeks
to
Make Your Test run on CI

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Assertions.*
assertThat(scoreStr).isEqualTo("Game won");
assertThat(list).anyMatch(e -> e.getX() == 1);
.doesNotContain(2);
.containsExactlyInAnyOrder(1,2,3);
.isEmpty();
assertThatThrownBy(() -> prod())
.hasMessageContaining("address");
+50 more
<dependency>
<groupId>org.assertj</groupId>
<artifactId>assertj-core</artifactId>
</dependency>
+60 more
Actual>Expected
Expected empty but was: <list.toString()>
Expressive Failure Message:
Testing Collections
Exceptions:
assertThat(list.stream().map(...))

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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

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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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Faster Spring Tests
1. Tune JVM: -ea -noverify -mx2048m -XX:TieredStopAtLevel=1
Debugging Test Context reuse: logging.level.org.springframework.test.context.cache=DEBUG
4. Reuse Contexts: reduce no of Spring Banners on Jenkins
6. Disable/Limit Auto-Configuration
2. Lazy-Load only Tested Beans: spring.main.lazy-initialization=true
3. Disable Web: @SpringBootTest(webEnvironment = NONE)
https://stackoverflow.com/a/49663075
= +30 sec test run time
5. Run in parallel

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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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WireMock

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WireMock.stubFor(get(urlEqualTo("/some/thing"))
.withHeader("Accept", equalTo("text/xml"))
.willReturn(aResponse()
.withStatus(200)
.withHeader("Content-Type", "application/json")
.withBody("[{"id":12, "value":"WireMock"}]")));
B) Programmatically
{
"request": {
"method": "GET",
"url": "/some/thing"
},
"response": {
"status": 200,
"body": "Hello WireMock!",
"headers": {
"Content-Type": "text/plain"
}
}
}
A) via .json config files:
Templatize content
from a .json file on disk
Record them
from real systems
http://wiremock.org/docs/running-standalone/
WireMock

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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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files
databases
queues
web services
Integration Tests

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Unit Tests
Integration
Deep
many layers
Fast
eg. 100 tests/sec
Slow
app startup,
network
... or Slow
in-mem DB, Spring,
Docker
Tiny
fine-grained
extensive mocks
Fragile
DB, REST APIs, files

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