Spring Boot makes it easy to setup and start a microservice project. But in microservice’s world, it is hard to test changes in all architecture. Because it is hard to setup same environment in local. So each service should responsible their own changes and guarantee that it won’t break any RPC call or business logic with new changes. Integration tests help in that manner to release the changes in more confident. So it is important to create an environment which is as much as close to production.
Testcontainers is a java library which rely on junit and docker containers. Any external dependency may included in testcontainer if it has a docker image.
Before testcontainers embedded or in memory solutions are exist for databases, message queues, etc. Testcontainers are different from in memory solutions, because it provides the ability to run the tests as much as close to production environment. On the other hand nowadays the services are running in containers. So it is a great ability to run the tests in docker containers too.
Assume a web application are using Postgres database. Developer want to test new feature which save some data to some tables and the query it from some others. Before testcontainers, to test the changes with integration tests developer should configure the postgres in her local machine. Ideal case it should be configures in continues integration(CI) environment too. Another approach may use the in memery solutions but in that case tests will be running different environment that production. Another problem is keeping the local database performance and isolation. Also it takes a lot of time to setup and maintenance. Testcontainers are solve all these problems.
In demo project, integration tests are using Spring tests and testcontainers. To see all dependency, you may take a look to build.gradle file.
testImplementation 'org.springframework.boot:spring-boot-starter-test'
testImplementation 'org.testcontainers:postgresql:1.10.6'
Created a configuration class for integration tests dependency beans. PostgreSQLContainer and DataSource beans are created in
IntegrationTestConfiguration class. Also need to set the DataSource bean as @Primary, because application context initialize
a default data source and in IntegrationTestConfiguration created another one. So it should know which one is injected primarily.
Another important file is embedded-postgres-init.sql. It is a using to initialize the database. In our example
there are two statements as one of them create hibernate_sequence, which is a requirement for AbstractPersistable, and
another one is just creating the product table. You may also want to run some insert queries before run your tests, so in that
case need to put all statements in that file which is required by test scenarios.
In the last step for the configuration, defined a base integration tests which is an abstract class and will be extended by other integration classes. It is a good practice to run your integration tests with a different profile, so below active profile is integration, which helps to isolate your integration tests application context from other profiles like development, test or production.
After configure the configuration and base classes then below is a simple example, an integration junit test which is
using testcontainers. In below scenario; just save a product via productRepository.save(product) and then query it from database
with productRepository.findByName(productName), then check the product names.
In this example, business logic keep it as simple, because it just focus how testcontainers is configured for integration tests. After configuration you may want to create more complex test scenarios with some other external storage or components too.
Also before run your tests check the docker first. Docker should be running at your machine otherwise you may see the error below;
Caused by: java.lang.IllegalStateException: Could not find a valid Docker environment. Please see logs and check configuration
You can find the all project on Github
https://www.testcontainers.org/
Happy coding :)