Random full coverage integration tests

[jpittis]

Build a “property testing” style integration test runner that generates a random set of events to apply to an in memory model and the snapshot cache, and then compare Envoy to the in memory model.

We need to support four cases:

• SoT with single streams
• SoT with aggregated streams
• Delta with single streams
• Delta with aggregated streams

The tool will let you run of the above cases for either N random events or until the harness is manually stopped (which is useful for perf testing). The harness will generate and display a seed so that it’s reproducible if a run fails.

Preferably we’d like to support all resource types, but just clusters and endpoints would be a good start.

The main test loop will look something like:

• Generate N random events
• Apply them to the model
• Apply then to the cache
• Compare Envoy to the model

As far as event types:

• We must support add, remove, and update of resources.
• It would be cool to support forcibly terminating the connection and/or restarting Envoy.

I’d also like to support testing ADS invariants and sending invalid config, but I’m not exactly sure how best to model that.

Otherwise, it would be cool to get the harness to spawn 1-N Envoy clients so we can use the same code for perf testing.