Test Propositional Formula Parser

[pmbittner]

Currently, we have a test for the boolean abstraction in src/test/java/CPPParserTest.java, which tests that C preprocessor directives are correctly abstracted to boolean formulas (as strings). However, there are no tests yet, that these strings are then (in a second step) indeed parsed correctly to a propositional formula AST as expected. The CPPParserTest should be extended by that, or there should be a new Test class.

This issue should be tackled once PR #103 is merged too avoid merge conflicts and redundant effort.

[pmbittner]

PR #103 was closed in favor of a revised PR #105 , which is now merged. So this issue can be tackled now.