Heroku - 13 Heroku Pipelines Tests
When you change code in a pipeline, you want to be sure the new version does not break features that already work. That validation is usually delivered through automatic tests: every time new code lands, a test suite is run, and the deploy is allowed only if all tests pass. Heroku provides a service for that, integrated directly into the Pipeline view: it is called Heroku CI (Heroku Continuous Integration).
How Heroku CI works inside a Pipeline
The flow is simple. On every code change, Heroku CI creates a brand-new application — a fresh, isolated test environment — runs your test suite against it, then destroys everything once the run is finished. Roughly speaking, each commit you push triggers a brand-new ephemeral environment that executes the new code. You can also configure the pipeline so that the code is promoted to the next stage only if every test passes. These automatic tests are extremely useful to make sure you never deploy code containing known bugs to the main application.
You can also tune the dynos used to run the tests. This matters when your build is large and takes a long time to test: by giving the test app larger or more dynos, you cut the test run time and therefore the time to ship. Note that Heroku CI configurations are per-application inside the pipeline, so you can require certain tests to pass before deploying app A while letting app B deploy directly without going through the same test gate.
Language and framework agnostic — the TAP protocol
Heroku CI can test practically every language and framework. This works because Heroku does not care about how your test runner decides what passes and what fails; it only cares about the exit code your test command returns at the end of the run, following the TAP (Test Anything Protocol) convention: 0 means all tests passed, and any other value (typically 1) means at least one test failed. As long as your framework can ultimately exit with a 0 or non-zero status, Heroku CI knows what to do with the result. See you in the next lesson.
Summary
This lesson explains how Heroku Pipelines implements automated testing to ensure new code doesn't break existing functionality. Heroku creates a temporary environment for each code change, runs tests, and destroys it afterward—allowing you to enforce deployment only when tests pass. The system supports any language or framework that returns Unix exit codes (0 for success, 1 for failure), and you can configure specific dynos for test execution to accelerate the testing phase.
Key points
- Automated testing validates code before production deployment, preventing bugs from reaching live applications
- Heroku Pipelines creates ephemeral test environments on every commit and destroys them after tests complete
- Continuous Integration enforces deployment gates: code deploys only if all configured tests pass
- Configure custom Dyno sizes for test execution to speed up the pipeline, especially for large builds
- Heroku works with any test framework using Unix exit protocol (exit code 0 = pass, non-zero = fail)
- Different applications in the same pipeline can have different test requirements and deployment rules
FAQ
Why would I want to enforce tests before deployment in Heroku Pipelines?
Enforcing tests prevents buggy code from reaching production, which could damage user experience and reliability. By making tests a deployment gate, you ensure every change is validated automatically before going live.
What frameworks and languages does Heroku's test integration support?
Heroku supports practically all programming languages and frameworks because it relies on the Unix exit protocol: as long as your test runner returns exit code 0 for success or 1 for failure, Heroku can run your tests regardless of the language or framework used.
How can I speed up my Heroku Pipelines tests?
You can configure custom Dyno sizes for test execution. Using more powerful dynos allows tests to run faster, which reduces the overall build time—especially beneficial for larger applications that require significant processing time for testing.