Selective testing

As your project grows, so does the amount of your tests. For a long time, running all tests on every PR or push to main takes tens of seconds. But this solution does not scale to thousands of tests your team might have.

On every test run on the CI, you probably build a project with cleaned derived data and re-run all the tests, regardless of the changes. tuist test helps you to drastically decrease the build time and then running the tests themselves.

Running tests selectively

To run tests selectively, use the tuist test command. The command hashes your project the same way it does for warming the cache, and on success, it persists the hashes on Tuist Cloud to determine what has changed in future runs.

In future runs tuist test transparently uses the hashes to filter down the tests to run only the ones that have changed since the last successful test run.

For example, assuming the following dependency graph:

• FeatureA has tests FeatureATests, and depends on Core
• FeatureB has tests FeatureBTests, and depends on Core
• Core has tests CoreTests

tuist test will behave as such:

Action	Description	Internal state
tuist test invocation	Runs the tests in CoreTests, FeatureATests, and FeatureBTests	The hashes of FeatureATests, FeatureBTests and CoreTests are persisted
FeatureA is updated	The developer modifies the code of a target	Same as before
tuist test invocation	Runs the tests in FeatureATests because it hash has changed	The new hash of FeatureATests is persisted
Core is updated	The developer modifies the code of a target	Same as before
tuist test invocation	Runs the tests in CoreTests, FeatureATests, and FeatureBTests	The new hash of FeatureATests FeatureBTests, and CoreTests are persisted

The combination of selective testing with binary caching can dramatically reduce the time it takes to run tests on your CI.

MODULE VS FILE-LEVEL GRANULARITY

Due to the impossibility of detecting the in-code dependencies between tests and sources, the maximum granularity of selective testing is at the target level. Therefore, we recommend keeping your targets small and focused to maximize the benefits of selective testing.