| CTEST_PARALLEL_LEVEL | |
| -------------------- | |
| .. include:: ENV_VAR.txt | |
| Specify the number of tests for CTest to run in parallel. | |
| For example, if ``CTEST_PARALLEL_LEVEL`` is set to 8, CTest will run | |
| up to 8 tests concurrently as if ``ctest`` were invoked with the | |
| :option:`--parallel 8 <ctest --parallel>` option. | |
| .. versionchanged:: 3.29 | |
| The value may be empty, or ``0``, to let ctest use a default level of | |
| parallelism, or unbounded parallelism, respectively, as documented by | |
| the :option:`ctest --parallel` option. | |
| On Windows, environment variables cannot be set to an empty string. | |
| CTest will interpret a whitespace-only string as empty. | |
| In CMake 3.28 and earlier, an empty or ``0`` value was equivalent to ``1``. | |
| See :manual:`ctest(1)` for more information on parallel test execution. | |