GitHub workflow for CI

[ahoenselaar]

Scope:

• C++ tests with MPI
• C++ tests without MPI
• Python v3.6 tests (MPI disabled) via pytest
• Python v3.9 tests (MPI disabled) via pytest

This is intended as an initial set up step.

The failing Python tests are going to be addressed in follow-up PRs. Issues identified so far include:

• Non-hermetic tests that break subsequent tests (verbosity_mgr)
• Memory corruption in pympb that causes later tests to fail

Other improvements for follow-up PRs:

• Cleaner presentation of test results
• Automatic inclusion of a "unit test badge" in PRs

[oskooi]

When running make check on my local machine for this branch, python/tests/test_simulation.py is failing with the following error:

======================================================================
FAIL: test_at_time (__main__.TestSimulation)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "./tests/test_simulation.py", line 142, in test_at_time
    self.assertTrue(os.path.exists(fname))
AssertionError: False is not true

======================================================================
FAIL: test_get_filename_prefix (__main__.TestSimulation)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "./tests/test_simulation.py", line 532, in test_get_filename_prefix
    self.assertEqual(sim.get_filename_prefix(), "simulation")
AssertionError: 'test_simulation' != 'simulation'
- test_simulation
? -----
+ simulation


======================================================================
FAIL: test_use_output_directory_default (__main__.TestSimulation)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "./tests/test_simulation.py", line 134, in test_use_output_directory_default
    self.assertTrue(os.path.exists(os.path.join(output_dir, self.fname)))
AssertionError: False is not true

======================================================================
FAIL: test_with_prefix (__main__.TestSimulation)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "./tests/test_simulation.py", line 162, in test_with_prefix
    self.assertTrue(os.path.exists(fname))
AssertionError: False is not true

----------------------------------------------------------------------
Ran 32 tests in 40.139s

FAILED (failures=4)

[stevengj]

What is going on with this change?

[ahoenselaar]

Before this change, only the $PY_PKG_FILES were copied to the meep folder.
In a second step, the MPB interface was added below.
However, the adjoint subpackage was never copied to meep.

Do you have any insight why that is the case?

[stevengj]

Our Python Makefile rules seem kind of hacky here; it would be better to rewrite them to cooperate with automake if possible.

[ahoenselaar]

Example output: https://github.com/ahoenselaar/meep/runs/2796065822

Shows a few broken tests and a segfault due to memory corruption.
Tests after the verbosity manager test fail but that will be addressed by #1602.