OPENNLP-1014: Add more tests for featuregen

[kojisekig]

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[coveralls]

Coverage increased (+0.5%) to 55.815% when pulling b1c2545 on kojisekig:featuregen-more-test into cb52b27 on apache:master.

[smarthi]

Can we do away with this method and instead use Assert.assertArrayEquals() ?

[kojisekig]

Thanks for the comment.

Of course I thought I should use Assert.assertArrayEquals() for the first time, but when I saw the result, I couldn't see any rule of the order of the set of ngrams. That's why I used contains.

I've not seen NGramModel in detail, which is used in CharacterNgramFeatureGenerator to generate the ngrams, but it seems that it uses Set (via Map.entrySet) to manage the set of ngrams and it causes that we cannot see any rule for the order of ngrams.

In order to use Assert.assertArrayEquals(), I should sort the result first, but I think it cannot be useful for the readability.

[smarthi]

+1 to merge