Instructions to run tests from the command line (#758)

* Instructions to run tests from the command line

* Remove shell wrapper note.
CL -> Common Lisp

Author: glennj

docs/TESTS.md

@@ -12,4 +12,21 @@ As you make changes to the solution you are writing use your editor's functional
 
 Remember to evaluate `(exercise-name-test:run-tests)` to re-run the tests after loading your updated solution.
 
+## Testing from the command line
 
+Executing the tests from the command line is possible, but it depends on which Common Lisp implementation you have chosen.
+For example, with SBCL you could execute this in the directory for exercise "foo"
+
+```sh
+sbcl --noinform \
+     --load foo-test \
+     --eval '(exit :code (if (foo-test:run-tests) 0 1))'
+```
+
+Other Common Lisp implementations will have similar but slightly different command-line options and exit commands.
+
+This assumes you have already installed SBCL and Quicklisp.
+See [Installing Common Lisp locally](https://exercism.org/docs/tracks/common-lisp/installation)
+
+That command is somewhat unwieldy.
+A method to wrap that into the `exercism` CLI is [shown here](https://glennj.github.io/exercism/cli).