Currently tests for curses mainly call different functions and methods in random order. Not all argument combinations are covered by tests and results are not checked. I also ran tests with 1750 different values of TERM supported by ncurses, and some tests were failed because not all features are supported on all terminals.

The proposed PR rewrites tests for curses.

* Added tests for every function or group of related functions.

* Added separate tests for optional functions, so that skipped tests are shown it output.

* Optionally skipped tests for functions like beep() and flush() which do not supported an all terminals (surprisingly!).

* Every function which takes variable number of arguments is now tested with all combination of arguments.

* Functions which support different types of argument (str/bytes/int) are now tested with all supported types.

* Function which change the global state are now called in order which restores presumably default value.

* Checked values and types of results of functions.

* Some tests serve role of demos. They call some function in some order and check how it affects results of other functions.

* Tests now work on terminals with small size (15 lines or less). Some terminals have very small default size.

It could still be improved (for example not all functions are tested with non-ASCII strings), but I spent several weekends (including a New Year and both Christmases) on this work and want to take a break.