I might have to create multiple

python_tests

targets with

name=test_unit

and

name=test_integration

plus tags and explicitly add the test modules to each target, as the solution for moment?

python_tests(
  name="tests",
  sources=["test_*.py", "!test_an_integration_test.py"]
)

python_tests(
  name="integration_tests",
  sources=["test_an_integration_test.py"],
  tags=["integration_tests"]
)

And then running unit tests/integration tests explicitly becomes...

# run unit tests
./pants -tag=-integration_tests test :: -- -m "not integration"

# run integration tests
./pants -tag=integration_tests test :: -- -m "integration"