Xtext: How do test the xtext lexer?

I have a list of terminals in my Xtext grammar how can I test that they work and that there are no token conflicts?

For example the following terminals:

terminal COMMA: ',';
terminal QUESTION: '?';
terminal IDENTIFIER: ('a'..'z'| 'A'..'Z')+;
terminal LENGTH: 'LENGTH' | 'l' | 'len';
terminal SEMICOLON: ';' ;