for example:
adding variable to context
seting variable values by multiple assignment


parsing, parsing, parsing!
I should begin with small things. For example... designing some input files, which 
then tokenized should be parsed. Really simple stuff. And then I should check AST. 
What actually has been build? Maybe for this kind of stuff visitor patter would be appropriate.

Visitor as a tester... hm... it goes around and remembers data. Different kinds of visitors. Not so bad 
idea, actually. But that imposes some change in design. Actually not so bad changes.

So - designing input file
parsing input, creating AST
visiting AST, and getting data from it, comparing acquired data to data, we want to get

Smaller parts like creating AST Nodes. I don't know, for example some parts of parser. Maybe those parts
should become standalone functions, to be tested more easily?

What's more?

My lexer doesn't have enough tests, i think. More tests! For example, given, acquired, desired.

And em, It'd be nice if I could run test from console like ./Sencha-lang --run-tests or something. Done.

Okay. Let's test some table manipulation.