Generate an HTML coverage report from coverage data.

Instruct the coverage tool to produce an HTML report for visual inspection of test coverage.

After running tests with coverage enabled, when a developer wants to inspect which lines of code were executed.

Within a Python test suite that uses coverage.py, after calling cov.start() before tests and cov.stop() after tests.

cov.html_report(directory='<path>')

cov.html_report(directory='<path>')

directory: str (path to output directory, default 'htmlcov')

• cov.start()
• cov.stop()
• cov.save()
• cov.report()

• directory='cov_html'
• directory='./coverage'
• directory='htmlcov' (default)
• directory='./htmlcov'

Forgetting to call cov.start() before tests leading to empty report; forgetting cov.stop() or cov.save() before generating report, resulting in incomplete data; specifying a non‑existent or inaccessible directory causing IOError; using relative paths that resolve incorrectly relative to the current working directory.

cov.report() – generates a terminal‑based coverage report; cov.xml_report() – produces an XML report for CI integration; cov.html_report(directory='cov', show_contexts=True) – includes contextual source lines in the HTML output.

Coming from Java's JaCoCo: may expect an XML report by default; remember to call html_report() for HTML output in Python's coverage.py.

• coverage reporting methods

The directory is created if it does not exist; the report includes source code with green/red highlighting; generation is fast after test execution but can be disk‑intensive for large projects; the report can be opened in any browser without a server.

Enables quick visual identification of untested lines, helping improve test coverage and code quality.

Think of html_report as developing a photograph of your test coverage – you expose the code with tests, then develop the picture into a viewable web page.

If the directory argument is omitted, coverage.py defaults to 'htmlcov'.

Consider using cov.html_report(directory='cov', show_contexts=True) for richer context, or switch to cov.xml_report() for XML reports suited to CI pipelines.