Ad hoc testing is performed to explore the different areas in the product by applying intuition, knowledge of the product, technology, domain and experience. It is done to find bugs that were not uncovered during planned testing.
Ad hoc tests may be run either prior to or after execution of planned tests. Ad hoc testing when done prior to planned testing helps in evaluating the quality of the product before starting a formal testing campaign. It also helps clarify requirements better.
Ad hoc tests when run post execution of planned tests helps unearth newer defects that planned tests may have missed. It highlights additional perspectives and scenarios which may not have been considered as part of the planned test exercise. Towards the end of the release after the formal test cycles have been run, a round of ad hoc testing serves to increase confidence in the coverage of the planned cycle.
While Ad hoc tests are executed without the need to document test cases, it is recommended to document tests that were executed and steps followed as much as possible to enable us to enhance the existing planned test suite, ensure repeat-ability and increase coverage.
In Ad hoc testing, the tester "improvises" and attempts to find bugs with any feasible means. An approach to ad hoc testing would be to start our tests using the existing documented test cases and explore newer variations from there. Alternatively, the tester(s) can explore the product using their experience and knowledge without referring to documented tests.
Ad hoc testing enables discovery - of new issues, areas that may not have been touched by planned tests, new perspectives that question requirements and assumptions. Ad hoc testing can find holes in your test strategy. Ad hoc testing when run post planned testing, serves as a tool for verifying the completeness of your testing.
A drawback of ad hoc testing is that these tests are not documented and, hence, not repeatable. This prevents ad hoc tests from being used for subsequent regression testing. To overcome this, it is recommended that we document test cases as much as possible once they have been executed. Despite this, it may be the case that some tests and steps may be left out as testers "jump" across functional areas to test and unearth issues. Ad hoc tests can be used to complement the planned testing exercise. On its own, it doesn't inspire much confidence in coverage. There is also the concern regarding repeat-ability despite trying to document as many of the tests and steps as possible.
Do you know the different types of testing? Check this post to know more.
