lcov_ex

Test coverage module to generate a lcov.info file for an Elixir project.

The docs can be found at https://hexdocs.pm/lcov_ex.

Why

Visualize line coverage

Many test coverage tools use lcov files as an input.

You can use it as I do to watch coverage progress in the following editors:

• VSCode:
  • Using the Coverage Gutters extension.
  • Using the Koverage extension (add "cover" in settings as coverage folder, or output the report to the "coverage" folder, see below).
• Atom, using the lcov-info extension (it requires you to change the output folder to "coverage", see below).

Please let me know if you made it work in your previously unlisted favorite editor. Or, if you're really nice, just add it to this list yourself 🙂

Coverage report in CI

You can use mix lcov --exit in a Github Action CI to safely run your tests and generate the lcov file, and then use that with a report tool to generate a comment with code coverage information in your pull requests.

See this project's CI configuration for more info on how to set it up.

Installation

Add to your dependencies:

  def deps do
    [
      {:lcov_ex, "~> 0.3", only: [:dev, :test], runtime: false}
    ]
  end

Usage

mix lcov

File should be created at ./cover/lcov.info by default.

Options

--quiet

To run silently use the --quiet option:

mix lcov --quiet

--output <folder>

To output the file to a different folder, use the --output option:

mix lcov --output coverage
...
Coverage file successfully created at coverage/lcov.info

--exit

Exits with a non-zero exit code if the tests fail: the same code that mix test would have exited with.

mix lcov --exit

Umbrella projects

By default, running mix lcov at the umbrella level will generate the coverage report for all individual apps and then compile them into a single file at ./cover/lcov.info.

--keep

For umbrella projects you can choose to keep the individual apps lcov files with the --keep option:

mix lcov --keep
...
Coverage file for my_app created at apps/my_app/cover/lcov.info
Coverage file for my_other_app created at apps/my_other_app/cover/lcov.info

Coverage file for umbrella created at cover/lcov.info

Run for single umbrella app

You can choose to run mix lcov for any single app inside an umbrella project by passing its folder as an argument.

mix lcov /apps/myapp

File should be created at ./apps/my_app/cover/lcov.info by default.

As test coverage tool

Alternatively, you can set up LcovEx as your test coverage tool in your project configuration:

  def project do
    [
      ...
      test_coverage: [tool: LcovEx, output: "cover"],
      ...
    ]

And then, run with:

mix test --cover

The output option indicates the output folder for the generated file.

Optionally, the ignore_paths option can be a list of path prefixes to ignore when generating the coverage report.

  def project do
    [
      ...
      test_coverage: [tool: LcovEx, output: "cover", ignore_paths: ["test/", "deps/"]]
      ...
    ]

TODOs

• Add missing FN lines, for the sake of completion.