The document outlines the importance of testing in Spring-based applications, highlighting various testing strategies and configurations. It discusses test cases, the significance of the test pyramid, and the use of testing annotations such as @ContextConfiguration and @SpringBootTest to facilitate isolated and effective testing. Additionally, it emphasizes best practices for leveraging Spring's testing tools and frameworks to create reliable software systems.

1. Testing
Spring-based
apps
Aleksandr Barmin
CONFIDENTIAL | © 2020 EPAM Systems, Inc.

2. 2020 EPAM Systems, Inc.
• Lead Software Engineer
• EPAM Lab Mentor
ALEKSANDR BARMIN
• Email: Aleksandr_Barmin@epam.com
• Twitter: @AlexBarmin
CONTACTS
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Agenda
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6
2
3
4
5
W H Y T E S T I N G I S S O I M P O R T A N T
C O N F I G U R I N G C O N T E X T F O R T E S T S
U S I N G R E A L D E P E N D E N C I E S
E X A M P L E S
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O V E R V I E W O F T E S T I N G
T E S T L A Y E R S

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Overview of testing
• A test case is a set of test inputs, execution
conditions, and expected results developed for
a particular objective, such as to exercise a
particular program path or to verify
compliance with a specific requirement.
• https://en.wikipedia.org/wiki/Test_case
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Test Suite
Overview of testing
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Test
Test
Test case
System Under
Test (SUT)
Verifies behavior of

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Overview of testing
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Test runner
Test class
Executes
Test method
Test method
Test method Teardown
Verify
Execute
Setup
Fixture
System Under
Test (SUT)
Configures
Restores
Interact

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Overview of testing
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Order Controller Order Service
Order Data Access
Object
Orders
Database
How to test it in isolation?

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Overview of testing
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Slow, complex
test
System Under
Test (SUT)
Dependency
Tests
Fast, simple
test
System Under
Test (SUT)
Test Double
Tests
Replaced with

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Why testing is so important – Test Pyramid
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End-to-
end
Component
Integration
UnitTest the business logic
Verify that a service
communicates with its
dependencies
Acceptance tests for a
service
Acceptance tests for an
application
Slow, brittle, costly
Fast, reliable, cheap

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Why testing is so important – the Ice Cream Cone
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End-to-end
Component
Integration
UnitTest the business logic
Verify that a service
communicates with its
dependencies
Acceptance tests for a
service
Acceptance tests for an
application
Slow, brittle, costly
Fast, reliable, cheap

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Deployment pipeline
Why testing is so important - The deployment pipeline
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Pre-commit
tests
Commit test
stage
Integration
tests stage
Component
tests stage
Deploy stage
Production
environment
Not
production
ready
Production
ready
Fast
feedback
Slow
feedback

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Talk is cheap. Show me the code
- Linus Torvalds
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The Blog Application
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Post Controller Post Service Post Repository Post Database

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Testing The Blog Application
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Post Controller Post Service Post Repository Post Database
PostServiceSpringTest

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@ContextConfiguration
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public @interface ContextConfiguration {
}

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@ContextConfiguration
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public @interface ContextConfiguration {
// where to find bean definitions
String[] value() default {};
String[] locations() default {};
Class<?>[] classes() default {};
}

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@ContextConfiguration
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public @interface ContextConfiguration {
// where to find bean definitions
String[] value() default {};
String[] locations() default {};
Class<?>[] classes() default {};
// how to initialize the Application Context
Class<? extends ApplicationContextInitializer<?>>[] initializers() default {};
}

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@ContextConfiguration
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public @interface ContextConfiguration {
// where to find bean definitions
String[] value() default {};
String[] locations() default {};
Class<?>[] classes() default {};
// how to initialize the Application Context
Class<? extends ApplicationContextInitializer<?>>[] initializers() default {};
// should context from parent classes be loaded
boolean inheritLocations() default true;
boolean inheritInitializers() default true;
}

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@ContextConfiguration
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public @interface ContextConfiguration {
// where to find bean definitions
String[] value() default {};
String[] locations() default {};
Class<?>[] classes() default {};
// how to initialize the Application Context
Class<? extends ApplicationContextInitializer<?>>[] initializers() default {};
// should context from parent classes be loaded
boolean inheritLocations() default true;
boolean inheritInitializers() default true;
// what will read bean definitions
Class<? extends ContextLoader> loader() default ContextLoader.class;
}

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@ContextConfiguration
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public @interface ContextConfiguration {
// where to find bean definitions
String[] value() default {};
String[] locations() default {};
Class<?>[] classes() default {};
// how to initialize the Application Context
Class<? extends ApplicationContextInitializer<?>>[] initializers() default {};
// should context from parent classes be loaded
boolean inheritLocations() default true;
boolean inheritInitializers() default true;
// what will read bean definitions
Class<? extends ContextLoader> loader() default ContextLoader.class;
// name of the context hierarchy level
String name() default "";
}

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@ContextConfiguration and @SpringJUnitConfig
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@ExtendWith(SpringExtension.class)
@ContextConfiguration(classes = {
PostService.class,
CommentValidator.class,
PostSanitizer.class
})
public class PostServiceSpringTest { }
@SpringJUnitConfig(classes = {
PostService.class,
CommentValidator.class,
PostSanitizer.class
})
public class PostServiceSpringTest { }

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@SpringBootTest
The search algorithm works up from the package that
contains the test until it finds a
@SpringBootApplication or
@SpringBootConfiguration annotated class. As long as
you’ve structured your code in a sensible way your main
configuration is usually found.
https://docs.spring.io/spring-
boot/docs/1.5.2.RELEASE/reference/html/boot-features-
testing.html#boot-features-testing-spring-boot-
applications-detecting-config
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@SpringBootTest
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Looks for
@SpringBootApplication or
@SpringBootConfiguration
@SpringBootConfiguration
@EnableAutoConfiguration
@ComponentScan(…)
public @interface SpringBootApplication { }
@SpringBootConfiguration
@Configuration
@TestConfiguration
PostControllerSpringBootTest

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@Sql, @SqlConfig and JdbcTestUtils
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@SpringBootTest(webEnvironment = WebEnvironment.RANDOM_PORT)
class PostControllerWithDbInitTest {
}

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@Sql, @SqlConfig and JdbcTestUtils
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@Sql(
scripts = "/create_posts.sql",
config = @SqlConfig(separator = ";")
)
@SpringBootTest(webEnvironment = WebEnvironment.RANDOM_PORT)
class PostControllerWithDbInitTest {
}

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@Sql, @SqlConfig and JdbcTestUtils
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@Sql(
scripts = "/create_posts.sql",
config = @SqlConfig(separator = ";")
)
@SpringBootTest(webEnvironment = WebEnvironment.RANDOM_PORT)
class PostControllerWithDbInitTest {
@Test
@Sql("/create_special_post.sql")
void findOne_shouldFindSpecialPost() {
// ...
}
}
ResourceDatabasePopulator populator = new ResourceDatabasePopulator();
populator.addScripts(new ClassPathResource("test-schema.sql"));
populator.setSeparator("@@");
populator.execute(this.dataSource);

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@Sql, @SqlConfig and JdbcTestUtils
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@Sql(
scripts = "/create_posts.sql",
config = @SqlConfig(separator = ";")
)
@SpringBootTest(webEnvironment = WebEnvironment.RANDOM_PORT)
class PostControllerWithDbInitTest {
@Autowired
private JdbcTemplate jdbcTemplate;
@Test
@Sql("/create_special_post.sql")
void findOne_shouldFindSpecialPost() {
final int postCount = JdbcTestUtils.countRowsInTable(jdbcTemplate, "POSTS");
assertTrue(postCount > 0);
// ...
}
}
PostControllerWithDbInitTest

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Testing The Blog Application
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Post Controller Post Service Post Repository Post Database
REST client

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Test layers - @JsonTest
• @JsonTest:
• CacheAutoConfiguration
• GsonAutoConfiguration
• JacksonAutoConfiguration
• JsonTestAutoConfiguration
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PostControllerJsonTest

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Testing The Blog Application
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Post Controller Post Service Post Repository Post Database
Web Client

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Test layers - @WebMvcTest
• @WebMvcTest:
• CacheAutoConfiguration
• MessageSourceAutoConfiguration
• HypermediaAutoConfiguration
• JacksonAutoConfiguration
• ThymeleafAutoConfiguration (*)
• ValidationAutoConfiguration
• ErrorMvcAutConfiguration
• HttpMessageConvertersAutoConfiguration
• ServerPropertiesAutoConfiguration
• WebMvcAutoConfiguration
• MockMvc(*)AutoConfiguration
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PostControllerWebMvcTest, AdminControllerHtmlTest

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Testing The Blog Application
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Post Controller Post Service Post Repository Post Database

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Test layers - @DataJpaTest
• @DataJpaTest:
• CacheAutoConfiguration
• JpaRepositoriesAutoConfiguration
• FlywayAutoConfiguration
• DataSourceAutoConfiguration
• DataSourceTransactionManagerAC
• JdbcTemplateAutoConfiguration
• HibernateJpaAutoConfiguration
• TransactionAutoConfiguration
• TestDatabaseAutoConfiguration
• TestEntityManagerAutoConfiguration
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PostRepositoryDataJpaTest

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Testing The Blog Application
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Post Controller Post Service Post Repository Post Database

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Test layers - @JdbcTest
• @JdbcTest:
• CacheAutoConfiguration
• FlywayAutoConfiguration
• DataSourceAutoConfiguration
• DataSourceTransactionManagerAC
• JdbcTemplateAutoConfiguration
• TransactionAutoConfiguration
• TestDatabaseAutoConfiguration
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PostJdbcTest

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Testing The Blog Application
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Post Controller Post Service Post Repository Post Database
External REST
Service

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Test layers - @RestClientTest
• @RestClientTest:
• CacheAutoConfiguration
• JacksonAutoConfiguration
• HttpMessageConverterAutoConfiguration
• WebClientAutoConfiguration
• MockRestServiceServerAutoConfiguration
• WebClientRestTemplateAutoConfiguration
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PostImporterRestClientTest

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Testing The Blog Application
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Post Controller Post Service Post Repository
Mock or in-
memory
database

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Docker Container
Testing The Blog Application
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Post Controller Post Service Post Repository
Real DB
instance
Mock or in-
memory
database

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TestContainers
• Integration tests with real dependencies in Docker
containers instead of mocks:
• Databases
• Message queues
• Browsers
• Anything else that could be run in Docker
• https://www.testcontainers.org/
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PostServiceTestContainersTest

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Examples weren’t shown
• @DertiesContext
• @ActiveProfiles
• @ContextHierarchy
• ReflectionTestUtils
• EnvironmentTestUtils
• Spring Cloud Contract
• Spring Cloud Stream Test
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Conclusion
• Follow the Test Pyramid approach
• Use FIRST for tests
• Use SOLID for your code
• Spring Framework has a lot of tools that simplify
testing – use them
• https://github.com/aabarmin/epam-spring-testing
• https://docs.spring.io/spring/docs/current/spring-
framework-reference/testing.html
• https://docs.spring.io/spring-
boot/docs/1.5.2.RELEASE/reference/html/boot-
features-testing.html
• https://www.testcontainers.org/
• https://spring.io/projects/spring-cloud-contract
• https://cloud.spring.io/spring-cloud-static/spring-
cloud-
stream/2.1.3.RELEASE/multi/multi__testing.html
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Thank you!

43. CONFIDENTIAL | © 2019 EPAM Systems, Inc.
QUESTIONS?
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