Experience-based testing techniques are adopted for several reasons, most importantly because they can identify defects that might be missed by more systematic approaches like black-box and white-box testing.
While systematic techniques follow predefined procedures and cover specific criteria, experience-based techniques leverage the tester's knowledge, intuition, and experience, which can be especially effective in uncovering subtle and complex issues.
Experience-based testing techniques include methods such as error guessing and exploratory testing. These methods rely on the tester's background and intuition to predict where defects might be located and how the system might fail. These techniques are particularly useful in situations where the requirements and specifications are incomplete or ambiguous, and where creative and ad-hoc approaches can provide significant value.
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* The official ISTQB CTFL syllabus emphasizes that experience-based techniques can find defects that more systematic techniques might miss, which makes them valuable complements to other testing methods.