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Bun’s test runner supports built-in code coverage reporting. This makes it easy to see how much of the codebase is covered by tests and find areas that are not currently well-tested.
Pass the --coverage flag to bun test to enable this feature. This will print a coverage report after the test run. The coverage report lists the source files that were executed during the test run, the percentage of functions and lines that were executed, and the line ranges that were not executed during the run.
terminal
bun test --coverage


test.test.ts:
✓ math > add [0.71ms]
✓ math > multiply [0.03ms]
✓ random [0.13ms]
-------------|---------|---------|-------------------
File         | % Funcs | % Lines | Uncovered Line #s
-------------|---------|---------|-------------------
All files    |   66.67 |   77.78 |
 math.ts     |   50.00 |   66.67 |
 random.ts   |   50.00 |   66.67 |
-------------|---------|---------|-------------------

 3 pass
 0 fail
 3 expect() calls
To always enable coverage reporting by default, add the following line to your bunfig.toml:
bunfig.toml
[test]
coverage = true # always enable coverage
Refer to Docs > Test runner > Coverage for complete documentation on code coverage reporting in Bun.
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