Test coverage

[nsbgn]

Test coverage should be automatically maintained via coverage.py.

Necessary tests separated by theme so as to have a hold on how to organize tests:

• type.py

  • Does type inference work?
  • Do subtype relations hold?
  • Are constraints minimized properly?
  • Do constraints raise errors at the appropriate times?

• expr.py

  • Can we compose expressions? Do the types check?
  • Are the types fixed at the appropriate times?
  • Are DeclarationErrors raised when they should?
  • Does printing expressions as strings work in the way we expect?

• lang.py

  • Can we parse everything we want? That is, inline typing, curried and uncurried functions, anonymous sources, labelled sources...
  • Are expressions printed as strings and then parsed equal to the original expressions?

• graph.py

  • Are expressions properly translated into graphs? What happens when a function is taken as parameter? What happens when that function contains variables? What happens when an expression can be expanded into primitives?

• query.py

  • Do queries work in all situations?

The above list is to be expanded.

[nsbgn]

Tests should also be simplified as I started doing in 12feaf3 and b2b9838.