# 33.5. Test Coverage Examination

The PostgreSQL source code can be compiled with coverage testing instrumentation, so that it becomes possible to examine which parts of the code are covered by the regression tests or any other test suite that is run with the code. This is currently supported when compiling with GCC, and it requires the `gcov` and `lcov` programs.

A typical workflow looks like this:

```
./configure --enable-coverage ... OTHER OPTIONS ...
make
make check # or other test suite
make coverage-html
```

Then point your HTML browser to `coverage/index.html`.

If you don't have `lcov` or prefer text output over an HTML report, you can run

```
make coverage
```

instead of `make coverage-html`, which will produce `.gcov` output files for each source file relevant to the test. (`make coverage` and `make coverage-html` will overwrite each other's files, so mixing them might be confusing.)

You can run several different tests before making the coverage report; the execution counts will accumulate. If you want to reset the execution counts between test runs, run:

```
make coverage-clean
```

You can run the `make coverage-html` or `make coverage` command in a subdirectory if you want a coverage report for only a portion of the code tree.

Use `make distclean` to clean up when done.

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