Make it possible to only run a subset of the simulator tests using the TEST_PATH variable

Suggested by @gendankenexperimenter

Makefile

@@ -80,7 +80,7 @@ simulator-tests: prepare-virtual
 	$(MAKE) -C tests all
 
 docker-simulator-tests:
-	BOARD_HARDWARE_PATH="$(BOARD_HARDWARE_PATH)" ./bin/run-docker "make simulator-tests"
+	BOARD_HARDWARE_PATH="$(BOARD_HARDWARE_PATH)" ./bin/run-docker "make simulator-tests TEST_PATH=\"${TEST_PATH}\""
 
 run-tests: prepare-virtual build-gtest-gmock
 	$(MAKE) -c tests

docs/development/testing.md

@@ -0,0 +1,32 @@
+This is not yet proper documentation about running or writing tests, just some rough notes.
+
+Kaleidoscope includes a simulator that can pretend (to a certain extent) to be a keyboard for the purpose of testing.
+
+On most UNIX-like systems, you can run Kaleidoscope's simulator tests by running
+
+```
+make simulator-tests
+```
+
+Our simulator currently has some weird linking issues on macOS, so the easiest way to run tests on macOS is using Docker.
+
+
+```
+make docker-simulator-tests
+```
+
+During development, when you may be running your tests very frequently, it's sometimes useful to run a subset of tests.
+
+You can control the directory that Kaleidoscope searches for test suites with the 'TEST_PATH' variable.
+
+To only run tests in subdirectories of the 'tests/hid' directory, you'd write:
+
+```
+make simulator-tests TEST_PATH=tests/hid
+```
+or
+
+```
+make docker-simulator-tests TEST_PATH=tests/hid
+```
+

tests/Makefile

@@ -4,7 +4,9 @@ LIB_DIR		:= ${build_dir}/lib
 
 libcommon_a	:= ${top_dir}/_build/lib/libcommon.a
 
-TESTS			?= $(shell find . -name 'sketch.ino' -exec dirname {} \;)
+TEST_PATH ?= tests/
+
+TESTS			?= $(shell find ${top_dir}/${TEST_PATH} -name 'sketch.ino' -exec dirname {} \;)
 .PHONY: clean cmake-clean all googletest
 
 all: ${TESTS}