Level Up Your Integration Testing With Testcontainers

Level Up Your Integration Testing
With Testcontainers
Dan Vega ⸱ @therealdanvega
Developer Advocate, VMware
⸺
Cora Iberkleid ⸱ @ciberkleid
Developer Advocate, VMware
⸺
Maria Gabriella Brodi ⸱ @BrodiMg
Staﬀ Solutions Engineer, VMware

Abstract - SpringOne Tour
Traditional approaches to integration testing—using shared, local, or in-memory databases—fall short for
today's modern developer.
Developers today are building cloud native distributed microservices and taking advantage of a rich variety
of backing services. This explosion of applications and backing services introduces new challenges in
creating the necessary environments for integration testing. To be useful and eﬀective, these environments
must be easy to create and they must resemble production as closely as possible. New solutions are needed
to make this need a reality.
Enter Testcontainers!
Testcontainers is a Java library that supports JUnit tests and makes it incredibly easy to create lightweight,
throwaway instances of common databases, Selenium web browsers, or anything else that can run in a
Docker container.

“You have to make the
right thing to do, the easy
thing to do.”
- Cora Iberkleid

Agenda
● Intro
● Testcontainers 101
● Spring Boot Demo
● Q&A

“Prod-like” integration testing - what do we mean?
● Integration vs Unit tests
● Greater fidelity to run-time conditions
○ Type of system
○ Network reliability
○ OS environment
● Shifted left
○ Local developer machine
○ Iterate locally

Common approaches to integration testing
In Integration tests we are interested in verifying the behavior and interactions of
multiple modules.
For this purpose we can use:
● Shared instances
● Local installation
● In memory solutions

In-memory testing
App
Mock server or
in-memory service
Options:
● Mock server (Wiremock, Loki…)
● In-memory service (h2, hsql...)

Limitations of in-memory testing
App
Mock server or
in-memory service
Limitations:
● Requires framework support
● Behavior diﬀerences to real system
● Latency/bandwidth testing can be
challenging
● Not every service has an in-memory
option
● Diﬀerences in security configuration

New challenges with in-memory testing
App
Challenge exacerbated with explosion in microservices
and variety of service options over the last 10 years.
Mock server or
in-memory service
Limitations:
● Requires framework support
● Behavior diﬀerences to real system
● Latency/bandwidth testing can be
challenging
● Not every service has an in-memory
option
● Diﬀerences in security configuration

Containerization Helps!
● Containerization per se is a big part of the solution
● Docker Compose - works for any framework
However…
● Cumbersome lifecycle management
● Additional skill set for developers to learn
However!
● There is an easier solution :)

Testcontainers: easy testing with external services
Service on Docker
App
Testcontainers
dependency

Testcontainers intro/overview
● Java library that creates instances of Docker containers for testing
● Supports JUnit4, JUnit5, and Spock

Support for other languages
(check GitHub for more complete information)

Available modules
● Provides lightweight,
throwaway instances of
common databases,
Selenium web browsers,
and more
● Can start anything else
that can run in a Docker
container
● Can run containers on
your local Docker or in
the Testcontainers Cloud
SaaS platform (beta)

Available modules
common databases,
and more

Available modules
common databases,
and more
● Can start anything else
that can run in a Docker
container
Whale by Artzgeo on Noun Project

And in the
cloud!
Testcontainers
Cloud
SaaS Platform (beta)
https:/
/testcontainers.cloud
Photo by Engin Akyurt on Unsplash
Whale by Artzgeo on Noun Project
X

Why Testcontainers? Where to use them?
● Prod-like systems:
● Easier instantiation of disposable services that lack an in-memory option
● Test against any application that can run as a container
● Integration testing:
● Data access layer integration
● Application integration
● Browser-based acceptance

package org.testcontainers.junit.jupiter;
import ...
class TestcontainersExtension implements BeforeEachCallback, BeforeAllCallback,
AfterEachCallback, AfterAllCallback, ExecutionCondition, TestInstancePostProcessor {
@Testcontainers (JUnit 5)
JUnit5 Extension - intercepts JUnit lifecycle
events and manages container lifecycles
@Testcontainers
public class MyIntegrationTests {
@Container // In JUnit 4, use @Rule/@ClassRule
static PostgreSQLContainer<?> db = new PostgreSQLContainer<>("postgres");
...
@ExtendWith({TestcontainersExtension.class})

@Container (JUnit 5) / @Rule (JUnit 4)
@Testcontainers
public class MyIntegrationTests {
@Container // In JUnit 4, use @Rule/@ClassRule
PostgreSQLContainer<?> db = new PostgreSQLContainer<>("postgres");
...
Flags TestcontainersExtension about a container to manage
● New container is started/stopped for every test
● Declare as static to re-use the same container

JUnit Test Lifecycle & Testcontainer Callbacks
BeforeAllCallback
BeforeEachCallback
AfterAllCallback
AfterEachCallback
ExecutionCondition
TestInstancePostProcessor

JUnit Test Lifecycle
@Testcontainers
@Slf4j
public class LifeCycleTest {
@Container
GenericContainer container = new
GenericContainer(DockerImageName.parse("myRepo/myImg"));
public LifeCycleTest() {
log.info("In Constructor. Class instance: ", this);
}
@BeforeAll
public static void beforeAllMethod() {
log.info("In @BeforeAll. Static method.");
}
@BeforeEach
public void beforeEachMethod() {
log.info("In @BeforeEach. Class instance: " + this
+ ", Container id: ", container.getContainerId());
}
@Test
public void test1() {
log.info("In @Test 1. Class instance: ", this);
}
@Test
}
@AfterEach
public void afterEachMethod() {
log.info("In @AfterEach. Class instance: ", this);
}
@AfterAll
public static void afterAllMethod() {
log.info("In @AfterAll. Static method.");
}
}

@Testcontainers
@Slf4j
@Container
}
@BeforeAll
}
@BeforeEach
}
@Test
}
@Test
}
@AfterEach
}
@AfterAll
}
}
In @BeforeAll. Static method.
No testcontainers
default action in
@BeforeAll
Test 1

@Testcontainers
@Slf4j
@Container
}
@BeforeAll
}
@BeforeEach
}
@Test
}
@Test
}
@AfterEach
}
@AfterAll
}
}
In Constructor. Class instance: LifeCycleTest@17d88132
No testcontainers action
in Constructor
Test 1

@Testcontainers
@Slf4j
@Container
}
@BeforeAll
}
@BeforeEach
}
@Test
}
@Test
}
@AfterEach
}
@AfterAll
}
}
Found Docker environment with local Unix socket (unix:///var/run/docker.sock)
Connected to docker
Pulling docker image: testcontainers/ryuk
Ryuk started - will monitor and terminate Testcontainers containers on JVM exit
Checking the system...
✔ Docker server version should be at least 1.6.0
✔ Docker environment should have more than 2GB free disk space
Pulling docker image: myRepo/myImg
Container myRepo/myImg is starting:
b1c63a2738a6131ac06dd90bc334e621099b8a9d0092cfbc8899954495bd57c5
In @BeforeEach. Class instance: LifeCycleTest@17d88132, Container id:
@BeforeEach, Test1:
Connect to docker
Start ryuk
Check system
Start container
Execute BeforeEach method
Test 1

@Testcontainers
@Slf4j
@Container
}
@BeforeAll
}
@BeforeEach
}
@Test
}
@Test
}
@AfterEach
}
@AfterAll
}
}
Connected to docker
In @Test 1. Class instance: LifeCycleTest@17d88132
in @Test
Test 1

@Testcontainers
@Slf4j
@Container
}
@BeforeAll
}
@BeforeEach
}
@Test
}
@Test
}
@AfterEach
}
@AfterAll
}
}
Connected to docker
In @AfterEach. Class instance: LifeCycleTest@17d88132
Ryuk removed container and associated volume(s): myRepo/myImg
After Test 1 “AfterEach”,
Ryuk cleans up container
Test 1

@Testcontainers
@Slf4j
@Container
}
@BeforeAll
}
@BeforeEach
}
@Test
}
@Test
}
@AfterEach
}
@AfterAll
}
}
Connected to docker
In Constructor. Class instance: LifeCycleTest@42d236fb
Constructor creates a
new class instance
Test 2
Test 1

@Testcontainers
@Slf4j
@Container
}
@BeforeAll
}
@BeforeEach
}
@Test
}
@Test
}
@AfterEach
}
@AfterAll
}
}
Connected to docker
20e4227f6d5366c7f6ccb2ebf09eb5666bb75d20a4c307c6026870dc0fc0d3a1
In @BeforeEach. Class instance: LifeCycleTest@42d236fb, Container id:
@BeforeEach, Test2:
Start new container
Execute BeforeEach method
Test 2
Test 1

@Testcontainers
@Slf4j
@Container
}
@BeforeAll
}
@BeforeEach
}
@Test
}
@Test
}
@AfterEach
}
@AfterAll
}
}
Connected to docker
In @Test 2. Class instance: LifeCycleTest@42d236fb
in @Test
Test 2
Test 1

@Testcontainers
@Slf4j
@Container
}
@BeforeAll
}
@BeforeEach
}
@Test
}
@Test
}
@AfterEach
}
@AfterAll
}
}
Connected to docker
In @AfterEach. Class instance: LifeCycleTest@42d236fb
In @AfterAll. Static method.
After Test 2 “AfterEach”,
Ryuk cleans up container
Test 2
Test 1

@Testcontainers
@Slf4j
@Container
}
@BeforeAll
}
@BeforeEach
}
@Test
}
@Test
}
@AfterEach
}
@AfterAll
}
}
Connected to docker
In @AfterEach. Class instance: LifeCycleTest@42d236fb
No testcontainers
default action in
@AfterAll
Test 2
Test 1

@Testcontainers
@Slf4j
@Container
static GenericContainer container = new
}
@BeforeAll
}
@BeforeEach
}
@Test
}
@Test
}
@AfterEach
}
@AfterAll
}
}

@Testcontainers
@Slf4j
@Container
static GenericContainer container = new
}
@BeforeAll
}
@BeforeEach
}
@Test
}
@Test
}
@AfterEach
}
@AfterAll
}
}
Connected to docker
8d8ff20a9f25dd8b0d4cd025406bdebfa9dcf5ab637ef53b5a815d97bc739b5a
In Constructor. Class instance: LifeCycleTest@63a5d002
In @BeforeEach. Class instance: LifeCycleTest@63a5d002, Container id:
In @Test 1. Class instance: LifeCycleTest@63a5d002
In @AfterEach. Class instance: LifeCycleTest@63a5d002
In Constructor. Class instance: LifeCycleTest@60e949e1
In @BeforeEach. Class instance: LifeCycleTest@60e949e1, Container id:
In @Test 2. Class instance: LifeCycleTest@60e949e1
In @AfterEach. Class instance: LifeCycleTest@60e949e1
Container is reused
across tests
Test 2
Test 1

Spring Boot ❤ Testcontainers
https://github.com/danvega/reading-list

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