readme

README.md

@@ -61,4 +61,15 @@ thinks::WritePgmImage("my_file.pgm", width, height, pixel_data.data());
 ```
 
 ## Tests
-Tests are implemented in the [Catch2](https://github.com/catchorg/Catch2) framework.
+The tests for this package are written in the [Catch2](https://github.com/catchorg/Catch2) framework, which is included as a submodule of this repository. Cloning recursively to initialize submodules is not required when using the functionality in this package, only to run the tests.
+
+Running the tests is simple. In a terminal do the following (and similar for `Debug`):
+```bash
+$ cd d:
+$ git clone --recursive git@github.com:/thinks/pnm-io.git D:/pnm-io
+$ mkdir build-pnm-io
+$ cd build-pnm-io
+$ cmake ../pnm-io
+$ cmake --build . --config Release
+$ ctest . -C Release --verbose
+```