Let's admit the truth. Testing is often an overlooked aspect of software development and an afterthought in most teams. There are very few developers who actively enjoy writing tests. Only a few know how to write automated tests effectively. Albeit we all admit and learned that testing helps ensure that our application is robust, reliable, and works as intended, there's not much traction in this area. In this article, we'll look at the most common testing Spring Boot testing best practices to provide a good starting point for testing enterprise Spring Boot applications.
Get Started with Testing
If we're new to testing, it can be overwhelming to figure out where to start. The good news is that Spring Boot makes testing our application easy. Before we get started with testing, we need to make sure we have a good understanding of the application we're testing and the fundamentals of testing with Spring Boot.
For example, what are the critical components of the application, and what are the possible failure scenarios? Having a clear understanding of the application's architecture will help you write more effective tests. Blindly testing every branch of our implementation is not the way to go.
Having tests in place is also an excellent way to provide documentation for our future self and team members. We can understand what the responsibility of a class is all about when taking a look at the corresponding tests.
When done poorly and only as an afterthought, the quality of our tests suffers. With a deadline ahead and little time left in the sprint, our team will be less likely to produce high-quality code thanks to a covering test suite.
It only takes one team member that decides to stop this bad practice and embrace good testing practices for a Spring Boot project.
Starting to Unit Test: Not as Hard as You Think* by Eric Dietrich is a great place to start and adjust one's mindset about testing.
Learn the Testing Fundamentals & Tooling
When it comes to testing, there are several fundamentals that we need to know. For example, we should understand the different types of tests, such as unit tests, integration tests, and end-to-end tests. Unit tests are used to test individual units or components of the application, while integration tests are used to test how different units or components work together. End-to-end tests, on the other hand, test the entire application as a whole.
We may be using different terms and scopes for our test strategy, but those these three types are a good place to start. Don't overcomplicate it. This may end up in religious discussion in which category to put a test and stealing precious development time.
Furthermore, every craftsman out there knows that they have to learn their toolbox to become an expert. Effective testing requires the correct use of testing frameworks and tools. In Spring Boot, several testing frameworks and tools are commonly used, such as JUnit, Mockito, and Spring Test. JUnit is a popular testing framework that provides a simple and easy-to-use interface for writing and executing tests. Mockito is a mocking framework that allows you to create mock objects for testing. Spring Test provides excellent testing support for Spring and Spring Boot applications.
To get started with the fundamentals of testing Spring Boot applications, start here:
- Things I Wish I Knew When I Started Testing Spring Boot Applications
- Maven Setup For Testing Java Applications
- Guide to Testing With the Spring Boot Starter Test
Don't Reinvent the Wheel
When it comes to testing, there's no need to reinvent the wheel. Spring Boot provides many pre-built tools and utilities for testing 0ur application. For example, we can use Spring's
TestRestTemplate to test your REST API endpoints, or Spring's
TestEntityManager to test any JPA-relared code.
Using pre-built tools not only saves time and effort but it also allows us to focus on the core functionality of our application. By leveraging these building blocks, we can ensure that our tests are comprehensive and effective.
Moreover, using pre-built tools can also help you avoid common pitfalls and mistakes that can occur when building custom testing utilities. The Spring Framework developers and community have already identified and addressed many of these issues, so we don't have to worry about them.
The same holds true for the testing tools and libraries we're using. There's a high chance that someone out there has already implemented a testing feature we're looking for. The Java testing ecosystem is huge and very mature. Take a look at the Java Testing Toolbox to make yourself familiar with it.
When in doubt, spend some time on Google or check Twitter/StackOverflow/Reddit before re-implementing an existing wheel.
Use Spring Boot Test Slices to Isolate Tests
When testing our application, we want our tests to execute fast. Nobody likes to wait 20 minutes for the build to pass to get feedback about an implementation or refactoring.
By narrowing the scope and isolating our tests, we prevent them from interfering with each other, making our tests run faster and more efficiently. Spring Boot provides test slices that allow us to isolate different parts of our application when testing.
One of the benefits of using test slices is that they allow us to focus on specific parts of your application. For example, the
@WebMvcTest slice will only load the components required to run MVC-based tests, such as controllers, filters, and views. This means that you can test your MVC application without the overhead of loading unnecessary components, making your tests faster and more efficient.
Another benefit of using test slices is that they make your tests more reliable. By isolating your tests, we reduce the chance of external factors affecting your test results. This means that we can be more confident in the accuracy of your test results.
While there are a lot of pre-defined test slice annotations coming with Spring Boot Test, the following articles provide a good starting point:
- Spring Boot Test Slices: Overview and Usage
- Spring Data JPA Persistence Layer Tests With @DataJpaTest
- MongoDB Testcontainers Setup for @DataMongoTest
Use the Spring TestContext Caching
When it comes to writing test cases, one of the most important things to consider is the speed and efficiency of the test suite. As a developer, we want to ensure that our tests run as quickly as possible without compromising on their accuracy and reliability. This is where the Spring TestContext caching mechanism comes into play.
When writing tests, it's not uncommon to create and tear down the same Spring context multiple times. Each time we create and tear down the context, it can take a considerable amount of time, slowing down our build.
By using the caching mechanism, we can significantly reduce the overhead of creating and tearing down the same Spring context multiple times. This can result in a much faster and more efficient test suite. The caching mechanism ensures that the context is created only once and then reused across multiple tests, thereby saving time and resources.
Another advantage of using the TestContext caching mechanism is that it allows you to maintain the state of the context across multiple tests. This means that any changes made to the context in one test will be available in the subsequent tests that use the same context. This can be particularly useful when testing complex applications that require a lot of setup and initialization.
It's worth noting that the caching mechanism is enabled by default. But there are many ways to work against this excellent feature. The most common one is using
More about the Spring TestContext caching mechanism:
- How fixing a broken window cut down our build time by 50%
- Improve Build Times with Context Caching from Spring Test
- Spring Test documentation
Summary of Spring Boot Testing Best Practices
By following the Spring Boot testing best practices we've outlined in this article, we can write effective and reliable tests for our Spring Boot application. The tools and features are available. It just takes some time to get used to them and a deliberate decision to improve the test setup.
In short, these are the mentioned Spring Boot testing best practices:
- Get started with testing in the first place
- Make yourself familiar with the fundamentals of testing Spring Boot applications
- Explore the Java Testing ecosystem
- Isolate tests using Spring Boot's test slices
- Speed up the test execution by making the most of the Spring TestContext context caching
Whenever you're ready, there are two ways I can help you further with testing Spring Boot applications: the Testing Spring Boot Applications Primer (beginner-friendly, 3 hours time investment) and the Testing Spring Boot Applications Masterclass (advanced, in-depth, and 10+ time investment).
*Marks affiliate links where I get a small cut if you buy through these.