Integration Tests in Test Pyramid
Discover techniques for enhancing test suites through integration testing, encompassing test environments, database adapters, web services, and consumer-driven contract testing.
In this section, we’re going to look at the next layer up in the test pyramid, integration testing. We’ll see why it’s important, review helpful tools, and understand the role of integration testing in the overall scheme of things.
Integration tests exist to test that our code will successfully integrate with external systems. Our core application logic is tested by unit tests, which, by design, do not interact with external systems. This means that we need to test behavior with those external systems at some point.
Advantages and limitations of integration tests
Integration tests are the second layer up in the test pyramid. They have advantages as well as limitations, as summarized in the following table:
Advantages and Limitations of Integration Tests
Advantages | Limitations |
They test that software components interact correctly when connected. | They require test environments to be set up and maintained. |
They provide a closer simulation of the software system as it will be used live | These tests run more slowly than unit tests. |
They’re susceptible to problems in the test environment, such as incorrect data or network connection failures. |
There should be fewer integration tests than unit tests. Ideally, far fewer. While unit tests avoided many problems of testing external systems by using test doubles, integration tests must now face those challenges. By nature, they’re more difficult to set up. They can be less repeatable. They generally run more slowly than unit tests do, as they wait for responses from external systems.
Optimizing test suite for reliable results
To give a sense of this, a typical system might have thousands of unit tests and hundreds of acceptance tests. In between, we have several integration tests. Many integration tests point to a design opportunity. We can refactor the code so that our integration test is pushed down to being a unit test or promoted to being an acceptance test.
Note: Another reason to have fewer integration tests is due to flaky tests. A flaky test is a nickname given to a test that sometimes passes and sometimes fails. When it fails, it is due to some problem interacting with the external system and not a defect in the code we’re testing. Such a failure is called a false negative test result, a result that can mislead us.
Flaky tests are a nuisance precisely because we cannot immediately tell the root cause of the failure. Without diving into error logs, we only know that the test failed. This leads to developers learning to ignore these failed tests, often choosing to rerun the test suite several times until the flaky test passes. The problem here is that we are training developers to have less faith in their ...