In some cases we has tests which are failed due to defect or environment issue. In this case we need to have ability to ignore such tests during calculating build result.
E.g. We have 100 tests and 1 test is failed due to defect which can be fixed in nearest future but we don't need to have builds unstable to see if another tests will nothing broke. In this case this test marked as "muted test" and we need to see that 99 tests are passed - build is ok and 1 test is muted.

Also need to have ability to unmute tests manually of in automatic way. I see such conditions to unmute tests:

• manually
• at date
• number of build from first failed build (where this test was failed)
• when it's fixed

Similiar functionality already exists in the TeamCity. You can read about this at this link - http://confluence.jetbrains.net/display/TCD7/Muting+Test+Failures