[ISTQB] 4.5 Experience-based Techniques (K2)

LO-4.5.1 Recall reasons for writing test cases based on intuition, experience and knowledge about common defects (K1) 

Error guessing, intuitive testing and exploratory testing are experienced-based techniques most of the times additionally applied on formal white or black box based techniques. These techniques are mainly depending upon tester's experience, knowledge and intuition.

Experience-based technique testing is particularly useful when there is few or inadequate system documentation and when there is short deadline for achieving testing activities. It requires testers with strong abilities (quick learner, good investigator), knowledge and experience for being effective.

LO-4.5.2 Compare experience-based techniques with specification-based testing techniques (K2)

Exploratory testing: is an "informal test design technique where the tester actively controls the design of the tests of those are performed and uses information gained while testing to design new and better test". Exploratory testing combines test design and test execution at the same time.
Information acquired on product exploration, test design, test execution (behavior), heuristics (guideline rules on the what and how) and recorded past results are logged and used as a lesson learnt for future tests. 

Fault attack: is "a structured approach to the error guessing technique enumerating a list of possible errors and to design tests that attack these errors."

Error guessing: is a non systematic technique based on tester's anticipation to enumerate a list of errors according to his experience (knowledge gained from previous similar projects for example) and to design test to attack these errors (fault attack defined previously)