The parallel test suite works by taking tests from the core suite and running them in parallel with each other. For behavior guarded by a feature flag named featureFlagToaster, jstests exercising this new feature can add the tag featureFlagToaster to ensure that the test is only run on all-feature-flags build variants and is excluded from multiversion testing. However, the parallel tester ignores this and attempts to run such tests even on non-feature-flag build variants.

Currently, the most simple workaround for this is to simply add each feature flagged test to the list of exclusions for the parallel tester, until the feature flag is enabled by default. However, for certain features this loss in test coverage may not be desirable.

If keeping the parallel test coverage is particularly important, another workaround is to explicitly check whether the feature flag is enabled on the server at the beginning of each test. If the server reports that the feature flag is not enabled, the test can simply return early before actually performing any testing. The downside to this is that it is more tedious and partially defeats the purpose of having the featureFlagToaster jstest tag to begin with.