1. A method comprising: receiving a first sequence of text element values, determining, with one or more computing devices, a value of a following text element, wherein determining the value of the following text element comprises: determining, based on the first sequence of text element values and a recurrent neural network trained with a corpus of text element values sequenced in accordance with a defined format, a probability value associated with a first text element value, wherein the probability value is related to the predictability of the first text element value following the first sequence of text element values based on a probabilistic model learned by the recurrent neural network from the corpus, comparing the probability value to a modification eligible threshold, and selecting either the first text element value or a second text element value as the value of the following text element based on whether the probability value exceeds the modification eligible threshold; processing, with the one or more computing devices, a second sequence of text element values with a set of instructions after determining that the probability value does not exceed the modification eligible threshold, the second sequence of text element values comprising the first sequence of text element values followed by the selected value of the following text element; and testing, with the one or more computing devices, a performance characteristic of the set of instructions when the set of instructions processes the second sequence of text element values, wherein testing a performance characteristic comprises determining whether there is a security issue associated with the set of instructions.