CollectCoverage

CollectCoverage refers to a configuration option used by certain test runners to collect code coverage data while tests are executed. When enabled, the test suite instruments the program code so that information about which statements, functions, and branches are exercised by tests is recorded. The resulting data are compiled into coverage reports that summarize how much of the codebase is covered by tests.

In practice, collectCoverage is typically toggled through a configuration setting or command-line flag. Enabling it usually causes the test runner to generate a set of coverage reports, often placed in a dedicated coverage directory. Common report formats include textual summaries, HTML dashboards, and machine-readable formats such as JSON or LCOV.

A key configuration related to collectCoverage is collectCoverageFrom, which specifies the files to include in coverage calculations. This allows excluding non-source files (such as tests or configuration files) or including specific subsets of the codebase. Other related options control where reports are written (coverageDirectory) and which report formats to emit (coverageReporters). Some environments also support coverage thresholds that enforce minimum coverage levels, causing a test run to fail if thresholds are not met.

Usage is most associated with JavaScript testing tools like Jest, which exposes collectCoverage as a boolean in its configuration and as a command-line option (--coverage). However, similar concepts exist in other coverage tools and ecosystems, often under different names. Collecting coverage provides insight into testing gaps, guiding improvements in test suites while potentially impacting test performance due to instrumentation.