Tests for dynamic latency and related metrics

[baranovmv]

I propose to test LatencyTuner specifically and the overall receiver pipeline in different tests. This task describes tests for LatencyTuner in isolation: check how LatencyTuner drives target latency depenging on incoming metrics.

Naturally we test here optimal latency estimation and the behavior of a state machine integrated into LatencyTuner in conjunction.

• In order to test latency estimation and decision making we could put LatencyTuner into situations where:
  • Decreasing is enabled iff current latency is significantly greater optimal latency estimation. Resulting target latency gets into --min/max-latency limits and it does not equal to optimal latency estimation, but conforms to a formula described in related comments in the source code.
  • Increasing is enabled more or less immediately when it is needed, and resulting target latency gets into --min/max-latency limits.
• For state machine we check that transition happens if aforementioned conditions met and certain timeout passed.
  • From the beginning up to startup timeout period no transition takes place
  • Decreasing and Increasing could happen only from idle state and then specific timeouts should pass before transition back to idle state happens.