Signed-off-by: Damien George <damien@micropython.org>

Default to just calling python since that is most commonly available: the
official installer or zipfiles from python.org, anaconda, nupkg all result
in python being available but not python3.  In other words: the default
used so far is wrong.  Note that os.name is 'posix' when running the python
version which comes with Cygwin or MSys2 so they are not affected by this.
However of all possible ways to get Python on Windows, only Cygwin provides
no python command so update the default way for running tests in the
README.

This commit switches the roles of the helper task from a cancellation task
to a runner task, to get the correct semantics for cancellation of
wait_for.

Some uasyncio tests are now disabled for the native emitter due to issues
with native code generation of generators and yield-from.

Fixes #5797.

Signed-off-by: Damien George <damien@micropython.org>

Signed-off-by: Damien George <damien@micropython.org>

The use of -S ensures that only the CPython standard library is accessible,
which makes tests run the same regardless of any site-packages that are
installed.  It also improves start-up time of CPython, reducing the overall
time spent running the test suite.

tests/basics/containment.py is updated to work around issue with old Python
versions not being able to str-format a dict-keys object, which becomes
apparent when -S is used.

Signed-off-by: Damien George <damien@micropython.org>

So they can be skipped if __rOP__'s are not supported on the target.  Also
fix the typo in the complex_special_methods.py filename.

Signed-off-by: Damien George <damien@micropython.org>

A configurable result directory is advantageous because it enables
using a dedicated location, eventually outside of the source tree,
instead of forcing the output files into a fixed directory which might
also contain other files already. For that reason the default output
directory also has been changed to tests/results/.

Replace some usages of paths relative to the current working directory
with absolute paths relative to the tests directory.

Fixes and resulting changes:
- default values of MICROPYTHON and MPYCROSS are absolute paths and
  always correct
- likewise, the correct full paths for tools and extmod directories
  are appended to sys.path
- printing/cleaning failures works properly since it expects the .exp
  and .out files in the tests directory which is also where they
  are written to now, plus no more need for changing directories

This fixes #5872 and allows running custom tests which use run-tests
without having to cd to the tests directory first, and the test output
still is in the tests/ directory instead of the current working directory.

Discovery of tests and all skip test logic based on paths relative to
the current working directory remains unchanged which essentially means
that for running most of MicroPython's own tests, run-tests must still
be ran from within it's directory, so document that.

This allows complex binary operations to fail gracefully with unsupported
operation rather than raising an exception, so that special methods work
correctly.

Signed-off-by: Damien George <damien@micropython.org>