cov shows code coverage data for your program in emacs. Currently, it supports gcov, lcov, coverage.py, and clover output, as well as the Coveralls format produced by undercover.el.

cov is on MELPA. To install it, type M-x package-install RET cov RET

Enable cov-mode in a buffer. It will use the methods in cov-coverage-file-paths to look for a suitable coverage data file. cov-mode uses file watchers to automatically reload the coverage file when it has been updated.

Line coverage is displayed in the left fringe and added to the help-echo text property of the line.

By default, cov will run in profiling mode. Lines which are executed a lot will have the fringe decorated with cov-heavy-face, while lines executed less will have the fringe decorated with cov-med-face and cov-light-face. Lines not executed at all will be decorated with cov-none-face.

Use the cov-high-threshold and cov-med-threshold variables to customize where the limits between haevy, medium, and light execution should be.

Setting cov-coverage-mode to t before enabling cov-mode will run cov in coverage mode. In this mode lines will be marked with cov-coverage-run-face or cov-coverage-not-run-face to executed and non-executed lines respectively. Coverage mode should make finding uncovered lines slightly easier than profiling mode.

Coverage files are located using the methods in cov-coverage-file-paths, a list of paths or functions that are tried in order to find a matching coverage file for the current buffer.

Paths can be used for coverage files which have the same name as the source file but with a suffix added, like gcov. So far gcov is the only supported tool that uses this scheme, but more can be added by appending to cov-coverage-alist. cov-coverage-alist bind postfixes to the coverage tools:

(setq cov-coverage-alist '((".gcov" . gcov)))

For other tool or more complex environments it is also possible to provide a function instead of a path string. The function will be called with the path and name of the buffer file and should return a cons cell of the form (COV-FILE-PATH . COVERAGE-TOOL). PATH shall be the full path and name of the coverage data file. COVERAGE-TOOL shall specify the coverage tool.

gcov files are located using cov-coverage-file-paths as described above.

An lcov tracefile can contain data for multiple source files and can be named anything. There are two ways to find tracefiles.

1. Set cov-lcov-file-name to the absolute path of the tracefile. This can be done with a directory- or file-local variable.

2. Add pattarns or functions to cov-lcov-patterns. Relative or absolute file patterns like "../lcov.info" will be tested in order to find a matching file. Functions takes the dir and name of the source file as arguments and should return an absolute path.

Coveralls file are named coverage-final.json and are searched for in each directory from the source file to the root.

Clover file are named clover.xml and are searched for in each directory from the source file to the root.

coverage.py file are named coverage.json and are searched for in each directory from the source file to the root.

cov.el can be extended to understand more coverage formats. To add a new format:

1. Add a function to cov-coverage-file-paths that locates a coverage file for a given file. If a coverage file is found, it should return a cons of the coverage file path and an identifier, like (cons filepath 'mytool). The original name of the file can be found in the cov-coverage-file buffer local variable.
2. Implement a cov--mytool-parse. The parse function is called with a temp buffer with the coverage file data as (current-buffer) and should parse the data and return the coverage as a alist of files to coverage mapping. Coverage data is simply a list of two element lists, where the first element is the line number and the second the coverage count.

Install dependencies:

cask install

Run tests:

cask exec ert-runner

GPLv3+