Work in progress - Code coverage tooling for Elm
elm-coverage is a tool for calculating code coverage for Elm code tested with
elm-test.
The goal of the reports generated by elm-coverage is to help you visualize
what parts of your code are being evaluated when running your tests, and to try
and guide you towards writing tests that focus specifically on the more complex
functions in your codebase.
The goal is not to condense that information down into a single metric. It is too easy to write tests that don't make meaningful assertions about your code and its behaviour, but only serve to increase the coverage.
The only thing worse than having no tests is having tests that provide a false sense of security.
For further reading, please direct yourself to https://elm-coverage.readthedocs.io
Installing elm-coverage works much the same way as installing other tools in
the Elm ecosystem:
npm i -g elm-coverage
The simplest invocation of elm-coverage is to simply invoke elm-coverage in
the root of your project:
elm-coverage
By default, elm-coverage assumes that your sources exist in a separate src/
directory, that you have elm-test installed globally, and that elm-test
needs no further, special flags.
You can specify an alternative path to crawl for sources to instrument:
elm-coverage elm_src/
If you don't want to use a globally installed elm-test, you can specify the
path to an elm-test executable:
elm-coverage --elm-test ./node_modules/.bin/elm-test
Parameters following -- are passed through to elm-test, for example to
specify the initial seed and number of fuzz testruns:
elm-coverage -- --seed 12345 --fuzz 99
elm-coverage will write an HTML report to .coverage/coverage.html. It is not
recommended to version control this directory. In order to open the report once
it is generated, you can specify the --open option:
elm-coverage --open
Issues and source code is available on
github. The source for
elm-instrument which is used to actually instrument the sources in order to
calculate coverage is also
available.
elm-coverage is licensed under the BSD-3 license. elm-instrument is
licensed under the BSD-3 license.