(c) Dr. Wolfgang J. Schneider GENERAL TESTING PRINCIPLES Dr. Wolfgang J. Schneider 2003 – 2006

(c) Dr. Wolfgang J. Schneider Acknowledgement Most of the content has been developed by ISTQB and its affiliates for fair use. The copy right of those parts is with them. The layout has been developed by us.

(c) Dr. Wolfgang J. Schneider General Testing Principles INTRODUCTION Over the past 40+ years, a number of testing principles have been suggested by different authors. They offer general guidelines common for all testing.

(c) Dr. Wolfgang J. Schneider General Testing Principles Testing shows Presence of Defects Testing shows Presence of Defects Exhaustive Testing is Impossible Exhaustive Testing is Impossible Early Testing Early Testing Defect Clustering Defect Clustering Pesticide Paradox Pesticide Paradox Testing is Context Dependent Testing is Context Dependent Absence-of-Errors Fallacy Absence-of-Errors Fallacy

(c) Dr. Wolfgang J. Schneider General Testing Principles Testing shows Presence of Defects Testing shows Presence of Defects Exhaustive Testing is Impossible Exhaustive Testing is Impossible Early Testing Early Testing Defect Clustering Defect Clustering Pesticide Paradox Pesticide Paradox Testing is Context Dependent Testing is Context Dependent Absence-of-Errors Fallacy Absence-of-Errors Fallacy

(c) Dr. Wolfgang J. Schneider General Testing Principles Testing shows Presence of Defects Testing shows Presence of Defects Exhaustive Testing is Impossible Exhaustive Testing is Impossible Early Testing Early Testing Defect Clustering Defect Clustering Pesticide Paradox Pesticide Paradox Testing is Context Dependent Testing is Context Dependent Absence-of-Errors Fallacy Absence-of-Errors Fallacy

(c) Dr. Wolfgang J. Schneider General Testing Principles Testing shows Presence of Defects Testing shows Presence of Defects Exhaustive Testing is Impossible Exhaustive Testing is Impossible Early Testing Early Testing Defect Clustering Defect Clustering Pesticide Paradox Pesticide Paradox Testing is Context Dependent Testing is Context Dependent Absence-of-Errors Fallacy Absence-of-Errors Fallacy

(c) Dr. Wolfgang J. Schneider General Testing Principles Testing shows Presence of Defects Testing shows Presence of Defects Exhaustive Testing is Impossible Exhaustive Testing is Impossible Early Testing Early Testing Defect Clustering Defect Clustering Pesticide Paradox Pesticide Paradox Testing is Context Dependent Testing is Context Dependent Absence-of-Errors Fallacy Absence-of-Errors Fallacy

(c) Dr. Wolfgang J. Schneider General Testing Principles Testing shows Presence of Defects Testing shows Presence of Defects Exhaustive Testing is Impossible Exhaustive Testing is Impossible Early Testing Early Testing Defect Clustering Defect Clustering Pesticide Paradox Pesticide Paradox Testing is Context Dependent Testing is Context Dependent Absence-of-Errors Fallacy Absence-of-Errors Fallacy

(c) Dr. Wolfgang J. Schneider General Testing Principles Testing shows Presence of Defects Testing shows Presence of Defects Exhaustive Testing is Impossible Exhaustive Testing is Impossible Early Testing Early Testing Defect Clustering Defect Clustering Pesticide Paradox Pesticide Paradox Testing is Context Dependent Testing is Context Dependent Absence-of-Errors Fallacy Absence-of-Errors Fallacy

(c) Dr. Wolfgang J. Schneider General Testing Principles Testing shows Presence of Defects Testing shows Presence of Defects Exhaustive Testing is Impossible Exhaustive Testing is Impossible Early Testing Early Testing Defect Clustering Defect Clustering Pesticide Paradox Pesticide Paradox Testing is Context Dependent Testing is Context Dependent Absence-of-Errors Fallacy Absence-of-Errors Fallacy

(c) Dr. Wolfgang J. Schneider General Testing Principles Testing shows Presence of Defects Testing shows Presence of Defects Exhaustive Testing is Impossible Exhaustive Testing is Impossible Early Testing Early Testing Defect Clustering Defect Clustering Pesticide Paradox Pesticide Paradox Testing is Context Dependent Testing is Context Dependent Absence-of-Errors Fallacy Absence-of-Errors Fallacy

(c) Dr. Wolfgang J. Schneider Testing shows Presence of Defects

(c) Dr. Wolfgang J. Schneider Testing shows Presence of Defects Testing can show you that defects are there. Testing cannot prove that there are no defects.

(c) Dr. Wolfgang J. Schneider Testing shows Presence of Defects Testing can show you that defects are there. Testing cannot prove that there are no defects.

(c) Dr. Wolfgang J. Schneider Testing shows Presence of Defects Testing can show you that defects are there. Testing cannot prove that there are no defects.

(c) Dr. Wolfgang J. Schneider Testing shows Presence of Defects

(c) Dr. Wolfgang J. Schneider Testing shows Presence of Defects Testing reduces the probability of undiscovered defects remaining in the software. But, even if no defects are found, it is not a proof of correctness.

(c) Dr. Wolfgang J. Schneider Testing shows Presence of Defects Testing reduces the probability of undiscovered defects remaining in the software. But, even if no defects are found, it is not a proof of correctness.

(c) Dr. Wolfgang J. Schneider Testing shows Presence of Defects Testing reduces the probability of undiscovered defects remaining in the software. But, even if no defects are found, it is not a proof of correctness.

(c) Dr. Wolfgang J. Schneider Testing shows Presence of Defects Testing cannot prove that there are no defects. If no defects are found, it is not a proof of correctness.

(c) Dr. Wolfgang J. Schneider Exhaustive Testing is Impossible

(c) Dr. Wolfgang J. Schneider Exhaustive Testing is Impossible Testing everything (all combinations of inputs and preconditions) is not feasible except for trivial cases. Instead of exhaustive testing, we use risk and priorities to focus testing efforts.

(c) Dr. Wolfgang J. Schneider Exhaustive Testing is Impossible Testing everything (all combinations of inputs and preconditions) is not feasible except for trivial cases. Instead of exhaustive testing, we use risk and priorities to focus testing efforts.

(c) Dr. Wolfgang J. Schneider Exhaustive Testing is Impossible Testing everything (all combinations of inputs and preconditions) is not feasible except for trivial cases. Instead of exhaustive testing, we use risk and priorities to focus testing efforts.

(c) Dr. Wolfgang J. Schneider Exhaustive Testing is Impossible Testing everything (all combinations of inputs and preconditions) is not feasible except for trivial cases. Instead of exhaustive testing, we use risk and priorities to focus testing efforts.

(c) Dr. Wolfgang J. Schneider Early Testing

(c) Dr. Wolfgang J. Schneider Early Testing Testing activities should start as early as possible in the software or system development life cycle They should be focused on defined objectives

(c) Dr. Wolfgang J. Schneider Early Testing Testing activities should start as early as possible in the software or system development life cycle They should be focused on defined objectives

(c) Dr. Wolfgang J. Schneider Early Testing Testing activities should start as early as possible in the software or system development life cycle They should be focused on defined objectives

(c) Dr. Wolfgang J. Schneider Early Testing Testing activities should start as early as possible in the software or system development life cycle They should be focused on defined objectives

(c) Dr. Wolfgang J. Schneider Early Testing Testing activities should start as early as possible in the software or system development life cycle They should be focused on defined objectives

(c) Dr. Wolfgang J. Schneider Defect Clustering

(c) Dr. Wolfgang J. Schneider Defect Clustering A small number of modules contain most of the defects discovered during pre-release testing, or show the most operational failures.

(c) Dr. Wolfgang J. Schneider Defect Clustering A small number of modules contain most of the defects discovered during pre-release testing, or show the most operational failures. A SMALL NUMBER OF MODULES CONTAIN MOST OF THE DEFECTS

(c) Dr. Wolfgang J. Schneider Pesticide Paradox

(c) Dr. Wolfgang J. Schneider Pesticide Paradox If the same tests are repeated over and over again, eventually the same set of test cases will no longer find any new bugs.

(c) Dr. Wolfgang J. Schneider Pesticide Paradox Most vintage testers call this the Mine Field Effect Mine Field Effect

(c) Dr. Wolfgang J. Schneider Pesticide Paradox To overcome this effect, the test cases need to be regularly reviewed and revised, and new and different tests need to be written to exercise different parts of the software or system to potentially find more defects.

(c) Dr. Wolfgang J. Schneider Testing is Context Dependent Testing is done differently in different contexts. For example, safety-critical software is tested differently from an e-commerce site.

(c) Dr. Wolfgang J. Schneider Testing is Context Dependent Testing is done differently in different contexts. For example, safety-critical software is tested differently from an e-commerce site.

(c) Dr. Wolfgang J. Schneider Testing is Context Dependent Testing is done differently in different contexts. For example, safety-critical software is tested differently from an e-commerce site.

(c) Dr. Wolfgang J. Schneider Testing is Context Dependent Testing is done differently in different contexts. For example, safety-critical software is tested differently from an e-commerce site.

(c) Dr. Wolfgang J. Schneider Testing is Context Dependent Testing is done differently in different contexts. For example, safety-critical software is tested differently from an e-commerce site. RISK

(c) Dr. Wolfgang J. Schneider Absence-of-Errors Fallacy Finding and fixing defects does not help if the system built is unusable and does not fulfill the users needs and expectations and expectations

(c) Dr. Wolfgang J. Schneider Absence-of-Errors Fallacy Finding and fixing defects does not help if the system built is unusable and does not fulfill the users needs and expectations

(c) Dr. Wolfgang J. Schneider Absence-of-Errors Fallacy Finding and fixing defects does not help if the system built is unusable and does not fulfill the users needs and expectations

(c) Dr. Wolfgang J. Schneider GENERAL TESTING PRINCIPLES

(c) Dr. Wolfgang J. Schneider General Testing Principles Testing shows Presence of Defects Testing shows Presence of Defects Exhaustive Testing is Impossible Exhaustive Testing is Impossible Early Testing Early Testing Defect Clustering Defect Clustering Pesticide Paradox Pesticide Paradox Testing is Context Dependent Testing is Context Dependent Absence-of-Errors Fallacy Absence-of-Errors Fallacy

DR. WOLFGANG J. SCHNEIDER GMBH International Information Technology Consultants Professional Testing Solutions Telecommunications and Utility Billing Systems Euro Preparation for Companies in New EU Member Countries EDIFACT – DATANORM – ELDANORM – ETIM Interfaces Data Exchange with Banks and Credit Card Companies Total Quality Management – Good Manufacturing Practices IT Service Management - IT Infrastructure Library (ITIL) Knowledge Management Solutions IT Fitness for GAAP – IAS – FASB Balanced Scorecard Take Advantage of 30+ Years of IT Experience ! Dr. Wolfgang J. Schneider - Start