Bazel: How to run py_binary to produce input files before testing

Question

I have a py_binary rule like this:

py_binary(
  name = "testInputs",
  srcs = ["testInputs.py"],
)

and a cc_test like this:

cc_test(
  name = "test",
  src = ["test.cc"],
  data = [":testInputs"],
)

test.cc needs an input file next to it (say input.txt) that is generated by testInputs.py. I want testInputs to get run and provide the input file to the test.

As mentioned here, I tried to to depend on testInputs in the data section. But the test doesn't find the input file nearby. Result of tree bazel-out | grep -F input.txt shows that even testInput rule has not run at all - since input.txt file not exists at all.

Answer 1

data = [":testInputs"] on the cc_test will make the py_binary itself available to the cc_test, not anything the py_binary might produce when run.

You'll want something like this:

cc_test(
  name = "test",
  src = ["test.cc"],
  data = [":test_input.txt"],
)

genrule(
  name = "gen_test_inputs",
  tools = [":test_input_generator"],
  outs = ["test_input.txt"],
  cmd = "$(location :test_input_generator) $@"
)

py_binary(
  name = "test_input_generator",
  srcs = ["test_input_generator.py"],
)