Adding base test_lexer class
Adding lexer_test test case
Adding test case for empty string
Adding lexer tests for id, keyword, space, id + space
Adding test class for testing combinators.py
Defining combinator_test method
Adding combinator tests for tags and reserved
Adding combinator tests for Concat
Adding combinator tests for exp parser
Adding combinator tests for alternate
Testing opt combinator
Testing rep combinator
Adding tests for process combinator
Adding test for lazy combinator
Testing phrase combinator