15. A computer program product comprising a non-transitory computer readable storage medium including computer usable code implemented in a computer system, for testing words defined in a pronunciation lexicon used in an automatic speech recognition system that is included in the computer system; wherein the computer usable code comprises: computer usable code for obtaining a plurality of test sentences which can be accepted by a language model used in the automatic speech recognition system, wherein the test sentences include a plurality of the words defined in the pronunciation lexicon; computer usable code for obtaining variations of speech data corresponding to each of the test sentences; computer usable code for obtaining a plurality of texts by recognizing the variations of speech data, or a plurality of texts generated by recognizing the variations of speech data; computer usable code for constructing a word graph, using the plurality of texts, for each of the test sentences, wherein each word in the word graph corresponds to each of the words defined in the pronunciation lexicon; and computer usable code for determining whether (i) all or (ii) parts of words in a test sentence of the test sentences are present in a path of the word graph derived from the test sentence.
18. The computer program product according to claim 15 , wherein each of the test sentences is generated together with feature information obtained from the language model and a number of the variations of speech data is determined according to the feature information.