add docs

README.markdown

@@ -77,6 +77,9 @@ The makefile in the root folder will make all utilities.
 TESTING
 -------
 
+To run tests automatically, ensure you have Docker and docker-buildx installed. Then run `./test/run_tests.sh`.
+
+Or to run tests manually:
 * Configure in 'build': `cmake -B build`
 * Install cram: `pipx install cram`
 * Run tests: `cram test/*.t`