Run Emscripten tests in a browser

[mcbarton]

Description

Please include a summary of changes, motivation and context for this PR.

This PR adds the ability to run the Emscripten tests in a browser

Fixes # (issue)

Type of change

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• Bug fix
• New feature
• Added/removed dependencies
• Required documentation updates

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 82.00%. Comparing base (66510a4) to head (d72f58a).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #294   +/-   ##
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  Coverage   82.00%   82.00%           
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  Files          20       20           
  Lines         950      950           
  Branches       87       87           
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  Hits          779      779           
  Misses        171      171           

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[mcbarton]

Without this MINIFY_HTML=0 flag you end up with the situation where the creation of the test_xeus_cpp.html file breaks on MacOS, but not Ubuntu as can be seen here https://github.com/compiler-research/xeus-cpp/actions/runs/14780201517

[mcbarton]

Running the tests makes use of emrun which comes with Emscripten. The documentation for emrun can be found here https://emscripten.org/docs/compiling/Running-html-files-with-emrun.html

[mcbarton]

The reason we install a fresh install of Firefox and Chome is to follow what is done in the Emscripten repo (for example here with Firefox https://github.com/emscripten-core/emscripten/blob/38e16464cffc8f886364fe4919a712131a4c9456/.circleci/config.yml#L363 ). It has the added advantage by not using the users installed versions of these browsers (if they have them installed), that there are no add ons, etc that could be causing issues with the tests running. I have made the instructions, such that a developer without admin privileges on there machine can install them.

[mcbarton]

Given emrun is not on our PATH, I have to reference the exact path to emrun.py . I could add ${{ env.BUILD_PREFIX }}/bin/ to PATH, but not sure if this would be wanted.

--kill_exit makes it so that when emrun finishes, that the headless browser we create is killed along with it
--timeout 60 is such that emrun is killed after 60 seconds if still running. emrun should have finished long before then, so if it is still running, something went wrong (such as a test which crashed the html file). This will cause the ci to fail, as a non 0 value of will be returned.

[mcbarton]

In the case of Chrome we have the extra --no-sandbox flag, as on Ubuntu Chrome will refuse to run otherwise, as it expects to have been installed with admin privileges. This flag allows it to run in userspace.

[mcbarton]

Rebuild your Emscripten application and add the --emrun [linker flag](https://emscripten.org/docs/tools_reference/emcc.html#emcc-emrun).

This flag injects code into the generated [Module object](https://emscripten.org/docs/api_reference/module.html#module) to enable capture of stdout, stderr and exit().

Note

If you skip this step, you can still run any .html file with emrun, but the capture will not work.

The above is taken from emruns documentation https://emscripten.org/docs/compiling/Running-html-files-with-emrun.html

[mcbarton]

So that we create a html file, as well as the javascript file.