1. A method performed 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 method comprises: 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; obtaining variations of speech data corresponding to each of the test sentences; 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; 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 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.