Error Guessing

Error Guessing

"A test design technique where the experience of the tester is used to anticipate what defects might be present in the component or system under test as a result of errors made, and to design tests specifically to expose them", per ISTQB.

Error guessing technique involves the tester making guesses about mistakes (errors) that a developer might make and then designing tests for them. Error guessing requires the tester to have knowledge and experience of common programming errors and their impact on code produced, the nature of bugs that can be introduced and how those may be reproduced. The tester needs to have some experience with programming and the technologies used by development. This enables the tester to make guesses about potential errors that may be introduced and create tests to find bugs associated with those errors. Error guessing may be used as a standalone technique or to complement other techniques. Error guessing can be applied at any stage of testing and may be used to even identify potential risks.

The effectiveness of using the Error guessing technique lay on the creativity and ability of the tester to guess errors and find bugs. Each tester is unique in this case and likely to approach this technique distinctly. Error guessing may also be used as a means to perform a quick smoke test. Trying to lay down guidelines and documentation requirements for this technique may constrain the tester's freedom and creativity which are important for Error guessing to be effective.

Needless to state it, error guessing is normally used as an additional test technique and not the sole or primary testing technique. Error guessing can help find bugs that may be missed by other techniques. Once tests are executed, it is recommended to capture them and automate as much as possible.

As you may have realized by now, the success of this technique to a certain extent is dependent on both the developer making similar mistakes as in the past and the tester having some experience with finding bugs that are similar to the ones that are in the current system-under-test.