Ad hoc vs Exploratory testing

Yet another interesting pair of testing terminology that are often mixed up or used as synonyms, although they should not be.

The confusion comes from the fact that many people believe that both 'Ad hoc' and 'Exploratory' testing are kind of random testing approaches where you just do whatever you want without any prior planning or set goals. This is not true, and let me debunk it for you.

My description

Ad hoc testing: is simply a one-time planned testing activity that does not rely on a prepared set of test cases. Primary goal is to quickly find obvious defects without a formal preparation and spending too much time on testing.

It is often executed in order to prove to the business, that the product is of acceptable quality.

The tester's domain knowledge and bug hunting skills are crucial factors.

Exploratory testing: primary aim is to learn about the system under test (SUT) and to document the results during execution, to ultimately create all the necessary testing documents (Test Plan & Strategy, Test Cases etc.). The tester prepares a checklist or mind map that he/she needs to follow during the execution.

As it requires great experience in testing, a proficient tester shall execute this type of testing.

Domain and platform knowledge are important factors in a successful Exploratory test.

Conclusion

In both approach the tester's skills and domain knowledge are crucial, and there is some form of freedom in how the tests are executed. But while 'Ad hoc' is not driven by any formal plans, only goals, 'Exploratory' testing follows a checklist and requires the tester to go as deep in testing as possible, to really explore the SUT.

ISTQB definitions

Ad hoc testing: "Informal testing performed without test analysis and test design."

Exploratory testing: "An approach to testing in which the testers dynamically design and execute tests based on their knowledge, exploration of the test item and the results of previous tests."

Reference: https://glossary.istqb.org

Last updated: April 19, 2025