more tests for visitor
CC for Context of vertex indexing
start to unit test vertex collector (the hard way)
refactor with provider and add test for interface
test for method vertex
test for param vertex
test for edge visitor
test for edge visitor : interface
doc for grammar
test for method edges
test for overriden method edge
refactor tests
factorizing the test
factoring mockup tests for edges
factoring fixtures for node
test method edge for interface
test for parameter edge
test edge to parameter
test edge for new instance
test edge for simple call