# Chaps

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A fork of [ExCoveralls]( focusing on the 100% coverage use-case.

## The 100% Coverage Use-Case

Shooting for 100% coverage is usually criticized as unnecessary and
unproductive, and we tend to agree with that sentiment. But as far as measuring
code coverage in percentage points goes, 100% is the only reasonable target:
any other percent-based target flaps around when SLOCs are added or removed.

Instead of shooting for a hard "we must get 100% coverage" rule, Chaps
recommends that you use ignores judiciously to avoid spending unnecessary
time trying to increase coverage, but still set the target coverage percentage
at 100%. This workflow sets a default "you must cover or ignore these lines"
mantra which forces code authors to be explicit.

This workflow also allows one to setup automated CI checks to fail when the
coverage is less than 100%, obviating the need to upload the coverage report
to an external service like coveralls.

## Installation

1. Add the dependency to your `mix.exs` `deps/0` function
1. Set the `test_coverage` tool in the `project/0` function
1. Set the `preferred_cli_env` to test for any tasks you intend to use

# mix.exs
def project do
    app: :my_app,
    version: "0.0.1",
    elixir: "~> 1.6",
    deps: deps(),
    test_coverage: [tool: Chaps],    #2
    preferred_cli_env: [             #3
      chaps: :test,
      "chaps.html": :test
    # ..

defp deps do
    {:chaps, "~> 0.1", only: :test}   #1

## Usage

Run `mix chaps` to run the test suite and show coverage. The output format
can be controlled by calling `mix chaps.<output format>` instead, where
`<output format>` can be any of

- `html`: an HTML based report showing coverage on source code
- `detail`: a terminal based output showing coverage on source code
- `json`, `xml`, or `lcov`: a JSON/XML/LCOV based data structure representing

## Configuration

Chaps is configured in `config/test.exs` like so

config :chaps,
  coverage_options: [
    treat_no_relevant_lines_as_covered: true

For the full schema, see the documentation of the `Chaps.Settings` module.

## Using ignores

Ignores in chaps are just about the same as they are in ExCoveralls:

# this piece of code is so hard to get meaningful coverage on that it's
# not worth our time, let's skip it

# chaps-ignore-start
def really_hard_to_get_coverage(args) do
  # ..
# chaps-ignore-stop

## Differences from `parroty/excoveralls`

- Coverage is truncated to the tenths place instead of rounded
    - this enforces that for even very large projects, 100% coverage means
      **all** SLOCs are covered, not just approximately all SLOCs
- Tasks and dependencies for uploading coverage reports have been removed
    - the `:hackney` dependency has been removed
- Configuration is done in `config/test.exs` instead of a JSON file
    - the `:jason` dependency is optional and is only used if running
      `mix chaps.json`

## License/Notice

This repository is a fork of
[`parroty/excoveralls`]( Almost
all source code originates from the original repository. See the `LICENSE`
file for attribution information.