gcov vs OpenClover

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.

OpenClover is a free code coverage tool for Java, Groovy and AspectJ. It tracks global, per-test and distributed per-test coverage using method, statement and branch metrics. More than 20 built-in code metrics are included, and custom metrics are supported. Coverage reports can be generated as HTML, XML, PDF, JSON or text. You can narrow coverage scope by paths, classes, methods, code blocks, statements, complexity or inline comments. For test optimization, OpenClover identifies tests to rerun when classes change, can run failing tests first, and can randomize test order. Integrations include Ant, Maven, Gradle, Grails, Griffon, Jenkins, Bamboo, Eclipse, IntelliJ IDEA, Sonar and JIRA. Dedicated test support covers JUnit 3 and 4, TestNG and Spock. Version 5.1.x supports JRE or JDK 8 through 25 and Groovy 3.x, 4.x and 5.x. The project is volunteer-maintained and Apache 2.0 licensed; community support typically responds within a few days.