How Did I Miss That Bug? Managing Cognitive Bias in Testing


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How many bugs have you missed that were obvious to others? We all approach testing hampered by our own biases. Understanding our biases—preconceived notions and the ability to focus our attention—is key to effective test design, test execution, and defect detection. Gerie Owen and Peter Varhol share an understanding of how the testers’ mindsets and cognitive biases influence their testing. Using principles from the social sciences, Gerie and Peter demonstrate that you aren’t as smart as you think you are. They show how to use knowledge of biases—Inattentional Blindness, Representative Bias, the Curse of Knowledge, and others—not only to understand the impact of cognitive bias on testing but also to improve your individual and test team results. Finally, Gerie and Peter provide tips for managing your biases and focusing your attention in the right places throughout the test process so you won’t miss that obvious bug.

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How Did I Miss That Bug? Managing Cognitive Bias in Testing

  1. 1.       nt Session    Presented by:  Gerie Owen, Northeast Utilities, Inc      Brought to you by:      340 Corporate Way, Suite   Orange Park, FL 32073  888‐2 T12  Concurre 4/8/2014    2:00 PM          “How Did I Miss That Bug?   Managing Cognitive Bias in Testing”      Peter Varhol, Telerik              300, 68‐8770 ∙ 904‐278‐0524 ∙ ∙ 
  2. 2. Gerie Owen Northeast Utilities, Inc   QA Consultant Gerie Owen specializes in developing and managing offshore test teams. Gerie has implemented the offshore model—developing, training, and mentoring new teams from their inception. She manages large, complex projects involving multiple applications; coordinates test teams across multiple time zones; and delivers high quality products. Gerie’s most successful project team wrote, automated, and executed more than 80,000 test cases for two suites of web applications, allowing only one defect to escape into production. In her everyday life, Gerie enjoys mentoring new test leads and brings a cohesive team approach to testing.
  3. 3. Peter Varhol Telerik   A testing evangelist at Telerik, Peter Varhol is a writer and speaker on software development and quality topics. Peter has authored dozens of articles on software tools and techniques for building applications, and has given conference presentations and webcasts on a variety of topics—user-centered design, integrating testing into agile development, and building the right software in an era of changing requirements. He has held key roles on engineering teams that have produced award- winning, quality tools such as BoundsChecker and SoftICE. Peter’s past roles include technology journalist, software product manager, software developer, and university professor.
  4. 4. 2/4/2014 1 How Did I Miss That Bug?How Did I Miss That Bug? OOOvercome Cognitive Bias Overcome Cognitive Bias  In TestingIn Testing Peter Varhol Gerie Owen Why are we talking about Why are we talking about  missing bugs?missing bugs?g gg g • Have you ever missed a bug? • Have you ever been asked how you missed a bug? • Have you ever wondered how you missed a bug?
  5. 5. 2/4/2014 2 Consequences of Missed Consequences of Missed  BugsBugs • Possible Consequences of Missed Bugs: o Negative Publicity o Lost Sales o Lost Customers o Even Loss of Life MISSED BUGS CAUSE MAYHEM My JourneyMy Journey The “HOW” is more important than the “WHY”The HOW is more important than the WHY And now , I invite you to join with me into the journey of How Did I Miss that Bug?How Did I Miss that Bug?
  6. 6. 2/4/2014 3 How Do We Miss Bugs?How Do We Miss Bugs? • Missed test casesMissed test cases • Misunderstanding of requirements • Misjudgment in risk-based testing • Inattention • Fatigue • Burnout • Multi-tasking How Do We Test?How Do We Test? • What is Software Testing?g o Software testing is making judgments about the quality of the software under test. o Involves: • Objective comparisons of code to specifications, • AND • Subjective assessments regarding usability, functionality etc
  7. 7. 2/4/2014 4 What IS What IS aa Missed Bug?Missed Bug? An Error in Judgment! To determine how testers miss bugs, we need to understand how humans make judgments, especially in complex situationsin complex situations.
  8. 8. 2/4/2014 5 How do we make How do we make  judgments?judgments? • Thinking, Fast and Slow – Daniel Kahneman o System 1 thinking – fast, intuitive, and sometimes wrong o System 2 thinking – slower, more deliberate, more accuratemore accurate System 1 vs. System 2 System 1 vs. System 2  ThinkingThinking • System 1 thinking keeps us functioning o Fast decisions, usually right enough o Gullible and biased • System 2 makes deliberate, thoughtful decisions o It is in charge of doubt ando It is in charge of doubt and unbelieving o But is often lazy o Difficult to engage
  9. 9. 2/4/2014 6 How Do We Apply System 1 How Do We Apply System 1  and System 2 Thinking?and System 2 Thinking? • System 1 thinking:• System 1 thinking: o Is applied in our initial reactions to situations. o May employ Heuristics or rules of thumb • System 2 thinking: o Is applied when we analyze a problem, for example when calculating the answer to a math problem. S t 1 d S t 2 b i fli t• System 1 and System 2 can be in conflict: o lead to biases in decision-making. The Lily Pad QuestionThe Lily Pad Question In a lake, there is a patch of lily pads. Every day, the patch doubles in size. If it takes 48 days for the patch to cover the entire lake, how long would it take for the patch to cover f fhalf of the lake?
  10. 10. 2/4/2014 7 How do Biases Impact How do Biases Impact  Testing?Testing? • We maintain certain beliefs in testing practice• We maintain certain beliefs in testing practice o Which may or may not be factually true o Those biases can affect our testing results o We may be predisposed to believe something that affects our work and our conclusions Ho do bias and error ork?• How do bias and error work? o We may test the wrong things o Not find errors, or find false errors The Representative BiasThe Representative Bias • Happens when we judge the likelihood of anHappens when we judge the likelihood of an occurrence in a particular situation by how closely the situation resembles similar situations. • Testers may be influenced by this bias when designing data matrices, perhaps not testing data in all states or not testing enough types of datain all states or not testing enough types of data. • Case Study: Completed Order bug
  11. 11. 2/4/2014 8 The Curse of KnowledgeThe Curse of Knowledge • Happens when we are so knowledgeable aboutpp g something, that our ability to address it from a less informed, more neutral perspective is diminished. • When testers develop so much domain knowledge that they fail to test from the perspective of a new user. Usability bugs are often missed due to thisuser. Usability bugs are often missed due to this bias. • Case Study: Date of Death Bug The Congruence The Congruence BBiasias • The tendency of experimenters to plan and executeThe tendency of experimenters to plan and execute tests on just their own hypotheses without considering alternative hypotheses. • This bias is often the root cause of missed negative test cases. Testers write test cases to validate that the functionality works according to the ifi ti d l t t lid t th t thspecifications and neglect to validate that the functionality doesn’t work in ways that it should not. • Case Study: Your negative test case or boundary miss
  12. 12. 2/4/2014 9 The Confirmation BiasThe Confirmation Bias • The tendency to search for and interpretThe tendency to search for and interpret information in a way that confirms one’s initial perceptions. • Testers’ initial perceptions of the quality of code, the quality of the requirements and the capabilities of developers can impact the ways in which they testdevelopers can impact the ways in which they test. • Case Study: Ability to print more than once bug The Anchoring The Anchoring EEffectffect • The tendency to become locked on and rely tooy y heavily on one piece of information and therefore exclude other ideas or evidence that contradicts the initial information. • Software testers do this often when they validate code to specifications exclusively withoutcode to specifications exclusively without considering ambiguities or errors in the requirements.
  13. 13. 2/4/2014 10 Inattentional BlindnessInattentional Blindness • Chabris and Simon conducted experiments on how focusing on one thing makes us blind to othersfocusing on one thing makes us blind to others o Invisible gorilla on the basketball court o Images on a lung x-ray Inattentional BlindnessInattentional Blindness • a psychological lack of attention • the tendency to miss obvious inconsistencies when focusing specifically on a particular task. • This happens in software testing when testers miss the blatantly obvious bugs
  14. 14. 2/4/2014 11 WWhy Do We hy Do We Develop Develop  BiasesBiases?? • The Blind Spot Bias o We evaluate our own decision-making process differently than we evaluate how others make decisions. • West Meserve and StanovichWest, Meserve and Stanovich Are you subject to Bias?Are you subject to Bias? A Test Planning Exercise This application is used to send a series of letters toThis application is used to send a series of letters to homeowners and renters to inform them of required inspections and get them to book appointments. The series are different based on whether the residence is a single or multi family and ends with a certified letter. The bug is that if the renter to whom the initial letter was sent moved the new renter would get the next letter in asent moved, the new renter would get the next letter in a series, potentially a strongly-worded certified letter when the series should start again from the first letter. This is a medium-severity defect; but high priority as it negatively affects customer experience.
  15. 15. 2/4/2014 12 How Does This Apply To How Does This Apply To  Testing?Testing? W t th• We must manage the way we think throughout the test process. oAs individual testersoAs individual testers oAs test managers oAs a professional community How Can Testers Manage How Can Testers Manage  Their Thought Processes?Their Thought Processes? • Use more System 1 thinking? OR • Use more System 2 thinking?
  16. 16. 2/4/2014 13 Test Methodology and Test Methodology and  System 2 ThinkingSystem 2 Thinking • Test methodology is the analyticalTest methodology is the analytical framework of testing; it invokes our system 2 thinking and places the tester under cognitive load. Th d t i ti f h th th t l• The determination of whether the actual results match the expected results becomes an objective assessment. HHow ow DDo o WWe e FFind ind BBugs?ugs? Focus on System 1 thinkingFocus on System 1 thinking, intuition and emotion
  17. 17. 2/4/2014 14 Focus On System 1 Focus On System 1  ThinkingThinking He ristics sed ith Oracles• Heuristics used with Oracles • Recognize our emotions as indicators of potential bugs • Exploratory Testing How Should We Use How Should We Use  Exploratory Testing?Exploratory Testing? • Unstructured o Before beginning test case execution • Minimizes preconceived notions about the application under test o Oracle basedo Oracle based • Users’ perspectives • Data flow
  18. 18. 2/4/2014 15 How Should We Use How Should We Use  Exploratory Testing?Exploratory Testing? • Structured o Use to create additional test cases • May be done earlier, possible as modules are developed o Session-Based • Time-boxed charters • Multiple testers • Post test review session What Can Test Managers What Can Test Managers  Do?Do? • Foster an environment in which the testers feel comfortable and empowered to use System 1 thinking. o Plan for exploratory testing in the test schedule o Encourage Testers to take risks o Reward for Quality of bugs rather than quantity of test cases executed
  19. 19. 2/4/2014 16 What Can the QA Profession Do?What Can the QA Profession Do? A Paradigm Shift A Paradigm Shift  o Shift our focus from requirements coverage based test execution to a more intuitive approach o Exploratory testing and business process flow testing becomes the norm rather than the exceptionexception o Develop new testing frameworks where risk- based testing is executed through targeted exploratory testing and is balanced with scripted testing Question Test ResultsQuestion Test Results • Is there any reason to suspect we are evaluating our test results based on self-interest, overconfidence, or attachment to past experiences? • Have we fallen in love with our test results? • Were there any differences of opinion among the team reviewing the test results?
  20. 20. 2/4/2014 17 How Do We Find The How Do We Find The  Obvious Bugs?Obvious Bugs? • Focus less • Use intuition • Believe what we can’t believe