Add instructions on how to run a subset of the tests

Makefile

@@ -40,7 +40,7 @@ clean-libs:
 
 test:
 	idris --build tests.ipkg
-	make -C tests only=$(only)
+	@make -C tests only=$(only)
 
 install: all install-exec install-libs
 

tests/Makefile

@@ -1,7 +1,7 @@
 IDRIS2 = ../../../idris2
 
 test:
-	../runtests $(IDRIS2) --only $(only)
+	@../runtests $(IDRIS2) --only $(only)
 
 clean:
 	find . -name '*.ibc' | xargs rm -f

tests/README.md

@@ -0,0 +1,13 @@
+Tests
+=====
+
+*Note: The commands listed in this section should be run from the repository's root folder.*
+
+Run all tests: `make test`
+
+To run only a subset of the tests use: `make test only=NAME`. `NAME` is matched against the path to each test case.
+
+Examples:
+- `make test only=chez` will run all Chez Scheme tests.
+- `make test only=ttimp/basic` will run all basic tests for `TTImp`.
+- `make test only=idris2/basic001` will run a specific test.