Add SimulationTest marker

[fabianschuiki]

The FIRRTL spec is about to define a simulation construct to indicate that a module should be executed as a simulation test. Add a user-facing SimulationTest class that can be used to mark a module as to be executed as a simulation test. This would commonly be used inside a test harness module to mark the surrounding module as a test. For example:

class TestHarness extends RawModule {
  SimulationTest(this)
}

The simulation test can be given an optional name and a map of parameters. The parameters are identical to the ones accepted by the FormalTest marker. Multiple simulation test markers may be added to a single module, which may be useful if a test should be run with different sets of user-defined parameters.

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Type of Improvement

• Feature (or new API)

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