CMake: decouple unit/integration test selection

[ouankou]

Summary

To run integration tests without forcing pFUnit, this PR adds two test-selection options and keeps backward compatibility with existing CMAKE_BUILD_TESTS workflows.

• Add BUILD_UNIT_TESTS to control pFUnit unit tests.
• Add BUILD_INTEGRATION_TESTS to control integration tests from examples/.

Behavior

• Default (no test flags): tests remain OFF (unchanged).
• -DCMAKE_BUILD_TESTS=ON: both test families default to ON (unchanged behavior).
• -DCMAKE_BUILD_TESTS=ON -DBUILD_UNIT_TESTS=OFF or -DBUILD_INTEGRATION_TESTS=ON: integration tests only.
• -DCMAKE_BUILD_TESTS=ON -DBUILD_INTEGRATION_TESTS=OFF or -DBUILD_UNIT_TESTS=ON: unit tests only.
• -DCMAKE_BUILD_TESTS=ON -DBUILD_UNIT_TESTS=OFF -DBUILD_INTEGRATION_TESTS=OFF: configuration fails with clear error.

[jatkinson1000]

Hi @ouankou

Thanks for this contribution and we feel it will be a useful feature.

I have a couple of requests/suggestions for you before we merge this.

• Please add FTORCH to the option names. This is so that when used as part of a larger build they are clear and do not conflict with other packages that might use the same commands.
• Could the logic be simplified whilst preserving behaviour, e.g. to:

  # Test selection
  if(CMAKE_BUILD_TESTS)
    set(_ftorch_tests_default ON)
  else()
    set(_ftorch_tests_default OFF)
  endif()
  
  option(BUILD_UNIT_TESTS "Build pFUnit-based unit tests" ${_ftorch_tests_default})
  option(BUILD_INTEGRATION_TESTS "Build integration tests from examples/" ${_ftorch_tests_default})
  
  # Enable tests if any test option is ON
  if(BUILD_UNIT_TESTS OR BUILD_INTEGRATION_TESTS)
    set(CMAKE_BUILD_TESTS ON)
  elseif(CMAKE_BUILD_TESTS)
    message(FATAL_ERROR
      "CMAKE_BUILD_TESTS=ON requires at least one of BUILD_UNIT_TESTS or BUILD_INTEGRATION_TESTS to be ON.")
  endif()

  ?
• We will also need some updates to the documentation around this. There is the main README.md, but then within pages/ there are installation/general.md and developer/testing.md that will need something adding.

[jatkinson1000]

This line fails CMake linting for being too long.

[jatkinson1000]

Hi @ouankou are you interested in making the above changes so that we can move towards merging this?

[ouankou]

Hi @ouankou are you interested in making the above changes so that we can move towards merging this?

Sure, I'll address the proposed changes accordingly. Thanks for the review!