Coveralls vs SimpleCov

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.

SimpleCov is a free, MIT-licensed tool for measuring Ruby code coverage with Ruby’s built-in Coverage library. It produces HTML and JSON reports and can merge results across test suites. Coverage types include line, branch, method, oneshot-line, and eval. Configuration supports filters, groups, profiles, and thresholds. Optional test tracking can show which RSpec examples or Minitest tests cover a line, while oneshot coverage can record code reached in production. The command line includes report viewing, test selection, patch coverage, history, status, and badge commands. A Rails profile can include ERB, Haml, and Slim templates in reports. SimpleCov can also calculate coverage for changed lines and apply a minimum threshold as a gate. The project says it is built in CI on Ruby 3.2+ and JRuby 10+; JRuby supports line coverage only. To track application files, SimpleCov must start before application code is required. The project directs code and bug reports to its issue tracker and discussion and announcements to its Google Groups mailing list.