Open source internal test runner

[keith]

Through a few conversations with Googlers I learned that internally a different test runner is used with rules_apple than the one that is publicly supported. I think because of this the open source version has a lack of testing which can cause issues that we likely wouldn't hit if the community shared the test runner that is currently used by Google. It would be great if that runner could be open sourced so that we could all contribute to it and improve a single tool, rather than being required to maintain our own test runners.

[sergiocampama]

This is something outside of the rules_apple project, but given the lack of an appropriate channel to make this request, we can keep it here for tracking.

[keith]

One thing I want to add to this is that iterating on / debugging xctestrunner is very difficult, here's the current steps I'm using:

1. Clone xctestrunner, subpar, and rule_apple
2. In your local xctestrunner checkout, merge these PRs: Update WORKSPACE for newer bazel versions google/xctestrunner#7 Rewrite imports for local builds google/xctestrunner#8
3. In your local subpar clone, change here and add "--interpreter", "/usr/bin/python2.7", (this may vary depending on how your project is configured, without this xctestrunner will try to work with python3, and if you change the par_binary rule and add python_version = "PY2" it will try to use the python2 executable which doesn't exist on macOS)
4. Build xctestrunner with bazel build //:ios_test_runner.par --override_repository=subpar=/path/to/subpar
5. Copy bazel-bin/ios_test_runner.par to your local bazel repo
6. In your repo's root BUILD file add:

filegroup(
    name = "foo",
    srcs = ["ios_test_runner.par"],
    visibility = ["//visibility:public"],
)

7. In your local rules_apple clone (or your custom test runner that uses xctestrunner), change all uses of @xctestrunner//file to //:foo
8. Test your code like normal passing --override_repository=build_bazel_rules_apple=/path/to/rules_apple

And repeat steps 4 and 5 whenever you make new changes to xctestrunner.

[jerrymarino]

👍 in the meantime, I've forked to ios-bazel-users