When a flag is set in fieldtrial_testing_config.json, there appears to be no way to clear it using the @CommandLineFlags annotation in a test.  This makes it very difficult to have tests for both true and false values when the config is set to true.  When the config is set to false, it is possible to override for an individual test.

For Contextual Search while developing CL 2506253002 I spent a lot of time trying different settings, and came to the above conclusion.  There is something called ParameterizedTest that may be able to handle this situation, but it seems complicated and I had trouble finding any good examples to guide its usage.