Add helper functions for unit test

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Add a helper function to create sample DFA. The function should accept a
string as the representation of the transitions.

Something like this: "ABa,ABb,BCa", which represents three transitions:
"A-->B" with "a" as input;
"A-->B" with "b" as input;
"B-->C" with "a" as input

Original issue reported on code.google.com by lemontree.cool on 6 Sep 2008 at 3:02

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Original comment by lemontree.cool on 6 Sep 2008 at 3:04

• Changed state: Accepted

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Original comment by lemontree.cool on 13 Sep 2008 at 12:42

• Changed state: Fixed