PlanRewriter Unit Tests

Test that the PlanRewriter correctly enforces run-time IRDAG optimizations in the runtime (annotation/reshaping by RunTimePasses) through appropriate rewrites of executing PhysicalPlans.

Two possible options for the test code (I am more leaning towards the former at the moment):

• Simulate the execution of PhysicalPlans (i.e., mocked Scheduler with simulated task events)
  • Pro: Simpler test code, smaller scope, a variety of simulations (fine-grained control) possible
  • Con: Does not test Executor code
• Actually execute PhysicalPlans with Executors
  • Pro: (Almost) Fully tests the compiler backend and the runtime
  • Con: May result in bloated test code, less control in execution steps 

The tests should include

• Run-time utility IRVertex insertion/deletion
• Run-time IRVertex/IREdge annotations
• Modifications to each category of ready/running/finished IRVertex objects