Coveralls vs gcov

Coveralls analyzes software test coverage, showing teams which code is not covered by tests. Its dashboard presents project coverage percentages and their changes over time, while repository views drill down from a project to sub-projects, files, and individual lines. Build history tracks coverage across branches, including pull requests. Coveralls can add summarized coverage results to pull requests and send status updates that apply coverage criteria to merge decisions. Notifications can go to Slack or webhooks. It supports line and branch coverage, with report formats including LCOV, SimpleCov, Cobertura, JaCoCo, and Clover XML. Coveralls says it works with any CI service and lists more than 30 community-created integrations, a GitHub Action, and a CircleCI Orb. An API can add repositories programmatically and return recent build statistics. Open-source and public repositories are free. The Starter plan is $10 a month for one private repository and includes a 30-day trial. A self-hosted enterprise installation can operate within existing security controls without outbound network access.

gcov is a free test coverage tool used with GCC to show how program code runs during testing. It reports which source lines execute and how often, producing per-line counts in `.gcov` files. Reports can include line, function, branch, condition, prime-path, and basic-block coverage. Options can report branch frequencies, show whether conditions independently affect a Boolean expression’s result, or filter reports to functions matching regular expressions. Output is available as `.gcov` text or gzip-compressed JSON; JSON generation does not require source code. The GCC documentation also describes using gcov with gprof to assess computing time, while warning that optimization can combine source lines and reduce hotspot detail. Before coverage reporting, programs must be compiled with GCC’s `--coverage` option. gcov works only with GCC-compiled code and is not compatible with other profiling or test coverage mechanisms. It runs on Linux, macOS, and Windows, supports the listed languages from C and C++ to Ada, D, and Go, and is self-hosted.