1. A computer implementable method of automatically generating, by a computer testing system, test data for testing a computer system, the test data including a character string, the method comprising: receiving, by the computer testing system, a signature of the character string to be generated, the character string comprising one or more words; dividing, by the computer testing system, the signature into a plurality of elements, each element being a numeric value indicative of a total sum of attribute values in a corresponding word in the character string, wherein each element in the signature maps to a respective word in the character string; for each element of the signature: generating, by the computer testing system, a combination of numeric values, such that a sum of the numeric values equals a value of the element, wherein the combination includes a predetermined number of numeric values; selecting, by the computer testing system, at least one combination of characters configuring the corresponding word from the character string, the selection being from a character table data-structure, and wherein the combination of characters is selected so as to achieve the determined total sum of attribute values for the corresponding word from the character string; in response to the character table data-structure including additional combinations of characters that match the determined total sum of attribute values, repeatedly selecting an additional combination of characters; and generating, by the computer testing system, the test data by including the selected combinations of characters; and using, by the computer testing system, the generated test data to test one or more operations of the computer system by using the test data as input.