Generate cover report for your crystal code coverage crystal-coverage spec
HEAD Latest release released


Coverage tool for Crystal lang


Before you start, you must understand this is a proof of concept. I'm not happy with the current code implementation.

Lot of features and options will change in the future.

The code will probably be rebuilt almost from scratch

Note also than it hasn't yet been properly tested. Ironic, for a cover tool, isn't it? :-) anyway, if you're bold enough to give a try, read the getting started below !


Just add this line in your shard.yml file

    github: anykeyh/crystal-coverage

Wait for the binary to compile. The binary will be build in bin/crystal-coverage


crystal-coverage spec/ spec/

Coverage file will be recreated after your software run on coverage/ folder.


There's probably dozen of bugs. Please fill issues and PR are welcome.

The library will evolve, so don't hesitate to shards update and test with the latest release before submitting an issue.

Due to some limitation, there's probably still a non-zero chance your code will not compile with the coverage instrumentations.

In this case, you can give a look to the generated output using the -p argument:

crystal-coverage src/ -p

When you fill issues, would be great to isolate the code which fail to load, so I can add it to my code library and fix the library.


The performances will slightly degrade using the coverage tool. Note the software is executed without release flag.

To test in --release mode, you can do:

crystal-coverage src/ -p | crystal eval --release

How does it works?

It uses ASTNode parsing to inject coverage instrumentations and reflag the lines of code using #<loc ...> directive

It covers only the relative files (e.g. require starting with .) inside your project directory.

It then generate a report in the directory /coverage/ relative to your project

Planned features

  • Binding with coveralls
  github: anykeyh/crystal-coverage
License MIT
Crystal none


Dependencies 0

Development Dependencies 1

  • ameba
    {'github' => 'veelenga/ameba'}

Dependents 1

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