Run Parallel Tests Using a New Option on the @isTest Annotation

Use the @isTest(isParallel=true) annotation to indicate test classes that can run in parallel and aren’t restricted by the default limits on the number of concurrent tests. This makes the execution of test classes more efficient, because more tests can be run in parallel.

This annotation overrides the default settings that disable parallel testing. A test class that doesn’t have this annotation is restricted by the default limits on the number of concurrent tests.