Verified the patch 2581431-settings-local-disable-test-discovery.patch mentio...

Verified the patch 2581431-settings-local-disable-test-discovery.patch mentioned in #3.
Steps followed:
1. Install D8 site.
2. Navigate to admin/modules and verify the Testing Group in the listing.
3. Apply the patch.
4. Repeat step 2.

Observation: Testing Group was present on link admin/modules even after the patch was applied.
NOTE: Please provide more detailed description of the issue. The above test was done as per my understanding of the issue