Problem:
We have a CMS which adjusts properties at different levels e.g. the level of the entire site and the level of the individual user. If the level of the individual user is not set, it inherits it from the company.

In order to test the functionality of the company settings, and the inherited properties, two separate tests are run. When both run simultaneously, as with the 2013 feature to distribute test lists across all available machines, one of the two tests will fail.

The feature I'm requesting is to give tests a specific property to identify which tests should not be run simultaneously. 

Suggested Implementation:
1 - Each test would be given a property, similar to the custom properties already implemented to assist with search.

2 - A new setting on executing a test list would be added: "avoid test collision"

3 - The execution server will queue tests with the same property back to back on the same machine to avoid collision.

Scenario 1:
Bob has 10 tests. Tests A through J.  He has 2-4 machines (Alpha, Beta, Charlie, Delta) on which to execute.
Tests "A, C, E, G, I" can not run together.
Tests "B, D" can not run together
Tests "F, H" can not run together
Test "J" can run at any time.

2 Machines:
Machine Alpha: A,C,E,G,I
Machine Beta: B, D, J, F, H

3 Machines:
Machine Alpha: A,C,E,G,I
Machine Beta: B, D, J
Machine Charlie: F, H

4 Machines:

Machine Alpha: A,C,E,G,I
Machine Beta: B, D,
Machine Charlie: F, H
Machine Delta: J