This allows querying the build system if there are test available.
Before, one should rely on 'info-debug-variable-TESTS' to print the list
of test files. But was not reliable as sometime the build system printed
messages anyway.
BOARD=esp32-wroom-32 make --silent --no-print-directory \
-C examples/hello-world/ info-debug-variable-TESTS
ESP32_SDK_DIR should be defined as /path/to/esp-idf directory
ESP32_SDK_DIR is set by default to /opt/esp/esp-idf
# empty line here
Now the return code can be trusted.
This commit adds a README.md to the testing folder.
It explains the basic about how to run a test with testrunner.
It adds a reference so it will be displayed on the doxygen docs.
There currently is not obvious documentation for running tests.
