testing.md: add testing doc

Doc is partly from Costin's original README and include details on the ctest
infrastructure and how to use

Signed-off-by: Brendan Le Foll <brendan.le.foll@intel.com>

docs/testing.md

@@ -0,0 +1,42 @@
+# Testing mraa
+
+Mraa has a test suite written in python which can be run by users to check
+their platform is working correctly. The aim is to have a full API coverage
+using python scripts using unittests. Currently the test suite is far from
+complete.
+
+## Supported platforms
+
+Intel Galileo v1 was used and is currently the only supported platform. Tests
+were conducted on Intel Galileo v2, but because of hardware differences, some
+failures may occur. Logic will be added to auto-select board to work on. To
+start with boards with an arduino type shield/layout should work
+
+## How to run these tests
+
+You need to compile from source with -DBUILDSWIGPYTHON=ON and then tests can be
+executed with:
+$ make test
+
+More detail can be seen by running:
+$ ctest -VV
+
+Note tests will not run on platforms which cannot initialise, checking the
+amount of 'skipped' tests can be useful
+
+## What's next?
+
+At this point tests were made to do a quick sanity check. In the future the
+followings will be implemented:
+ * Create a physical layer that will emulate sensors behavior and generate I/O
+   signals. This layer will be available to the community and will help replace
+   the need of specific sensors. The simplest solution will be chosen allowing
+   anyone to rapidly implement it.
+ * Implement stress tests over long periods of time. This feature alone is
+   possible only with the use of a physical layer since it will behave both as
+   signals generator and interpreter.
+ * Analyze a tests result collection solution (and after, interpretation). This
+   is useful since tests mean nothing without a history and possibility to
+   check on results.
+ * Any idea welcome!
+