We present a structured reformulation of the seminal algorithm for 
automatic generation of test cases for a context-free grammar.
Our reformulation simplifies the algorithm in several ways.  First, 
we provide a structured reformulation so that it is obvious where to 
proceed at each step.  Second, we partition the intricate third phase
into five functions, so that the discussion and comprehension of this 
phase can be modularized.  Our implementation of the algorithm provides 
information about the grammatic, syntactic and semantic correctness of 
the generated test cases for two important languages in use 
today: C and C++.

The results of our study of C and C++ highlight a lacuna latent in the 
research to date.  In particular, if one or more of the automatically
generated test cases is syntactically or semantically incorrect, then 
the confidence of structural "coverage" may be compromised for
the particular grammar-based tool under test.  Our ongoing work 
focuses on a solution to this problem.