Notes about the development of language-python

----------------------------------------------

Testing

-------

How to test the parser? What to test for?

Idea: round trip parsing:

parseAndPrint < test.py > out_1.py

It may not be the case that test.py == out_1.py, using string equality on the

contents of the python files. Even the ASTs might be different (eg

parenthesising, line numbers).

So we run printAndParse on the output:

parseAndPrint < out_1.py > out_2.py

Hypothesis: out_1.py and out_2.py will be identical source files: we've

reached a fixed point. If they are not equal then there is a bug in either

the parser or the pretty printer or both.

Issues: this combines testing of the parser and pretty printer. It may

be desirable to test them in isolation - but is it worth the extra

effort?

It is harder to test the parser in isolation because its output is an

AST. Constructing expected ASTs is tedious, even for small programs.