Introduction to Software Testing Workshop on Integrating Software Testing into Programming Courses Friday June 12, 2015

What is software testing? Software testing is the process of operating software under specified conditions, observing or recording the results and making an evaluation of some aspect of the software. (IEEE/ANSI std 610.12-1990)

Overview of Testing - Terminology Software testing is the dynamic verification of the behavior of a program on a finite set of test cases, suitably selected from the usually infinite execution domain, against the expected behavior. (Guide to the Software Engineering Body of Knowledge 2004 Version)

Does testing always involve running a program? Static Testing: Testing without executing the program. This include software inspections and some forms of analyses. Dynamic Testing: Testing by executing the program with real inputs

What is a successful test case? One that produces expected results? OR One that produces a failure?

What is a test case? E.g., What is one test case to test a program that classifies triangles? Test Case Values: The values that directly satisfy one test requirement Expected Results: The result that will be produced when executing the test if the program satisfies it intended behavior

Testing Concepts Test case components: Name – identifies the test case, it is a good idea to derive the name from the requirement being tested. Purpose – states the purpose of the test and relates it to the requirement (or scenario). Test set up – describe the h/w and s/w and environment required for a successful test. Input – description of the input data or commands. Expected output (or Oracle) – expected test results against which the output of the test is compared.

How do we know the right answer? The Oracle Problem From previous version of the system Checking by hand Simulations Checks for reasonableness

How much testing is enough? Testing can show the presence of errors but not their absence. Edsger Dijkstra

Errors Discovered over Time Number of errors Time

What is the difference between a fault and a failure? Software Fault: A static defect in the software Software Failure: External, incorrect behavior with respect to the requirements or other description of the expected behavior

What is the difference between testing and debugging? Finding inputs that cause the software to fail Debugging: The process of finding a fault given a failure

Important Terms Validation & Verification The process of evaluating software at the end of software development to ensure compliance with intended usage Verification: The process of determining whether the products of a given phase of the software development process fulfill the requirements established during the previous phase IV&V stands for “independent verification and validation” Introduction to Software Testing (Ch 1), www.introsoftwaretesting.com © Ammann & Offutt

How is unit testing different from integration testing? How is integration testing different from system testing?

Levels of Testing Unit Testing Integration Testing Refers to tests that verify the functionality of a specific section of code, usually at the function level. In an object-oriented environment, this is usually at the class level, and the minimal unit tests include the constructors and destructors. (wikipedia, 2010) Integration Testing Is any type of software testing that seeks to verify the interfaces between components against a software design. Components may be integrated in an iterative way or all together ("big bang"). (wikipedia, 2010)

Levels of Testing System Testing Testing a completely integrated system to verify that it meets its requirements. (wikipedia, 2010) See http://en.wikipedia.org/wiki/Software_testing

Unit Testing Focuses on the building blocks of the software system i.e., objects and subsystems. Many unit testing techniques have been devised including: equivalence testing, state-based testing, boundary testing, domain testing, control flow- based testing (statement, branch).

What kinds of errors do you tend to find in unit testing versus integration testing? Between integration testing and systems testing?

Who does acceptance testing?

What is the difference between white (or glass) box and black box testing? Deriving tests from external descriptions of the software, including specifications, requirements, and design White-box testing: Deriving tests from the source code internals of the software, specifically including branches, individual conditions, and statements Introduction to Software Testing (Ch 1), www.introsoftwaretesting.com © Ammann & Offutt

In what way is testing like sampling? Why is sampling needed? Is exhaustive testing possible?

What makes program more difficult to test? Complexity Why might models of programs be helpful to guide testing? What kinds of models?

Criteria Based on Structures and Models Graphs Logical expressions Input domain characteristics Syntactic structures Ammann & Offutt, Introduction to Software Testing

How can a control flow graph be used to find test cases? What are criteria that we could use with control flow graphs? Coverage: statement (node), branch, …

Control Flow Adequacy Criteria Flow graph Example: Source code public int Fun(int x){ k = 0; while (x <= 10 && k < 3){ if (x%2 != 0) k = k + 1; x = x + 1; } if (x < 0){ x = 10; return k; Entry A K=0 B F x<=10 && k<3 C G T F X<0 F x%2 != 0 D T T X = 10 K = 0 k=k+1 E H x=x+1 F return k I

1. Graph Coverage – Structural 6 5 3 2 1 7 4 Path Cover every path 12567 1257 13567 1357 1343567 134357 … Edge (Branch) Cover every edge 12567 1343567 1357 Node (Statement) Cover every node 12567 1343567 This graph may represent statements & branches methods & calls components & signals states and transitions Introduction to Software Testing (Ch 1), www.introsoftwaretesting.com © Ammann & Offutt

How can a data flow graph be used to find test cases?

1. Graph Coverage – Data Flow This graph contains: defs: nodes & edges where variables get values uses: nodes & edges where values are accessed def = {x, y} def = {a , m} def = {a} def = {m} 6 5 3 2 1 7 4 use = {x} use = {a} use = {y} use = {m} All Defs Every def used once 1, 2, 5, 6, 7 1, 3, 4, 3, 5, 7 Defs & Uses Pairs (x, 1, (1,2)), (x, 1, (1,3)) (y, 1, 4), (y, 1, 6) (a, 2, (5,6)), (a, 2, (5,7)), (a, 3, (5,6)), (a, 3, (5,7)), (m, 4, 7), (m, 6, 7) All Uses Every def “reaches” every use 1, 2, 5, 6, 7 1, 2, 5, 7 1, 3, 5, 6, 7 1, 3, 5, 7 1, 3, 4, 3, 5,7 Introduction to Software Testing (Ch 1), www.introsoftwaretesting.com © Ammann & Offutt

1. Graph - FSM Example Memory Seats in a Lexus ES 300 Guard (safety constraint) Trigger (input) Driver 1 Configuration Driver 2 [Ignition = off] | Button2 [Ignition = off] | Button1 sideMirrors () [Ignition = on] | (to Modified) lumbar () [Ignition = on] | Modified Configuration seatBottom () [Ignition = on] | seatBack () [Ignition = on] | Ignition = off New Configuration Driver 1 Driver 2 [Ignition = on] | Reset AND Button1 [Ignition = on] | Reset AND Button2 Introduction to Software Testing (Ch 1), www.introsoftwaretesting.com © Ammann & Offutt

Unit Testing – Statement Coverage Statement coverage – A set P of execution paths satisfies the statement coverage criterion iff for all nodes n in the FG, there is at least one path p in P s.t. n is on the path p. Whitebox testing technique. Generate test data to execute every stmt in the program at least once. Exercise: Indentify value(s) of x to execute every stmt in Fun(int x) at least once.

Unit Testing – Branch Coverage Branch coverage – A set P of execution paths satisfies the branch coverage criterion iff for all edges e in the FG, there is at least one path p in P s.t. p contains edge e. Whitebox testing technique. Generate test data to exercise the true and false outcomes of every decision. Exercise: Indentify value(s) of x to execute every branch in Fun(int x) at least once.

How do predicates add complexity to programs and thus to testing?

( (a > b) or G ) and (x < y) 2. Logical Expressions ( (a > b) or G ) and (x < y) Transitions Logical Expressions Program Decision Statements Software Specifications Introduction to Software Testing (Ch 1), www.introsoftwaretesting.com © Ammann & Offutt

( (a > b) or G ) and (x < y) 2. Logical Expressions ( (a > b) or G ) and (x < y) Predicate Coverage : Each predicate must be true and false ( (a>b) or G ) and (x < y) = True, False Clause Coverage : Each clause must be true and false (a > b) = True, False G = True, False (x < y) = True, False Combinatorial Coverage : Various combinations of clauses Active Clause Coverage: Each clause must determine the predicate’s result Introduction to Software Testing (Ch 1), www.introsoftwaretesting.com © Ammann & Offutt

Logic – Active Clause Coverage ( (a > b) or G ) and (x < y) 1 T F T 2 F F T With these values for G and (x<y), (a>b) determines the value of the predicate duplicate 3 F T T 4 F F T 5 T T T 6 T T F Introduction to Software Testing (Ch 1), www.introsoftwaretesting.com © Ammann & Offutt

How can knowledge of the input space help in sampling for testing?

Input Domain Characterization Describe the input domain of the software Identify inputs, parameters, or other categorization Partition each input into finite sets of representative values Choose combinations of values System level Number of students { 0, 1, >1 } Level of course { 600, 700, 800 } Major { swe, cs, isa, infs } Unit level Parameters F (int X, int Y) Possible values X: { <0, 0, 1, 2, >2 }, Y : { 10, 20, 30 } Tests F (-5, 10), F (0, 20), F (1, 30), F (2, 10), F (5, 20) Introduction to Software Testing (Ch 1), www.introsoftwaretesting.com © Ammann & Offutt

Unit Testing – Boundary Analysis Test cases are generated using the extremes of the input domain, e.g. maximum, minimum, just inside/outside boundaries, typical values, and error values. It is similar to Equivalence Partitioning but focuses on "corner cases“. Exercise: write test case input using boundary analysis for the getNumberDaysInMonth() method.

Unit Testing – Equivalence Partitioning Equivalence partitioning is a blackbox testing technique that minimizes the number of test cases. Possible inputs are partitioned into equivalence testing classes, and a test case is selected from each class. Assumption - system behaves in a similar way for all members of an equiv. class. Criteria used to determine equivalence classes: coverage, disjointedness, representation.

Unit Testing – Equivalence Partitioning Example: Valid inputs to test the getNumberDaysInMonth() method Equivalence class Value for month input Value for year input Months with 31 days, non-leap yrs. 7 (July) 1901 Months with 31 days, leap yrs. 1904 Months with 30 days, non-leap yrs. 6 (June) Months with 30 days, leap yrs. Months with 28 or 29 days, non-leap yrs. 2 (February) Months with 28 or 29 days, leap yrs.

4. Syntactic Structures Based on a grammar, or other syntactic definition Primary example is mutation testing Induce small changes to the program: mutants Find tests that cause the mutant programs to fail: killing mutants Failure is defined as different output from the original program Check the output of useful tests on the original program Example program and mutants if (x > y) if (x >= y) z = x - y;  z = x + y;  z = x – m; else z = 2 * x; if (x > y) z = x - y; else z = 2 * x; Introduction to Software Testing (Ch 1), www.introsoftwaretesting.com © Ammann & Offutt

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