Theory and Practice of Software Testing Chapter 14 Presman Software Testing Tactics

Testing objectives [MYE79] Testing is a process of executing a program with the goal of finding an error. A good test is one that has a high probability of finding an error

Good Testing Has a high probability of finding an error Is Not redudant Should be “best f breed” Should be neither too simple nor too complex

Testing Techniques Test information flow Test case design White box testing Basis path testing Black box Testing Equivalence Partitioning Boundary Value Analysis

Test Information flow testing Software configuration evaluation errors results Error rate data debug corrections testing Reliability model test configuration Predicted reliability Expected results

White-Box testing Sometime called Glass-box testing A test case design philosophy that uses the control program structure to derive test case Knowledge of the program is used to identify additional test cases

White-Box testing Objective is to exercise all program statements (not all path combinations) Every instruction Every decision A set of paths that meets these criteria is said to provide cover or complete cover

White-box testing

Basis Path Testing One of white box testing technique The objective of basis path testing is to derive a logical complexity measure of procedural design and defining a basis set of execution paths Test case derived to exercise the basis set to execute every statement in the program at least one time during testing

Basis Path testing Uses flow graph or program graph that shows nodes representing program decisions and vertex representing the flow of control Statements with conditions are therefore nodes in the flow graph Node is any point in the program where the control either joins, or forks or both Nodes are joined by edges or links

Contoh Program

Predicate Node Node that contain a conditiona Can be compound with logical operator : “and” / “or”

Independent Path (IP) Independent Path is any path through the program that introduces at least one new set processing statement or a new condition

A set of independent path 1-2-10-11-13 1-2-10-12-13 1-2-3-10-11-13 1-2-3-4-5-8-9-2-… 1-2-3-4-5-6-8-9-2-… 1-2-3-4-5-6-7-8-9-2…

Process to deriving Test Cases Map the design or code to the corresponding flow graph Compute the cyclomatic complexity of the resultant flow graph Identify a basis set of independent paths Prepare test cases that will force execution of each path in the basis set

Cyclomatic Complexity : V(G) Metric that provides a quantitative measure of logical complexity of a program Define the number of independent path in the basis set of a program The number of tests cases used to test all control statements equals the cyclomatic complexity

Compute Cyclomatic Complexity V(G) = R V(G)= P +1 V(G) = E –N +2 Where : R is the number of regions of the flow graph P is the number of logical expressions (or predicates node) E is the number of flow graph edges N is the number of flow graph nodes

Path 1 test case Specification of Inputs Value (k) = valid input, where k < i Value (i) = -999 where 2 i 100 Specification of Output (expected results): correct average based on k values and correct totals should be computed Note: This test case must be test as part of path 4, 5, and 6 tests

Path 2 test case Inputs Expected results: Value (1) = -999 Average = -999; other total at initial values

Path 3 test case Inputs Expected results: Attempt to process 101 or more values The first 100 values should be valid Expected results: correct average based on k values and correct totals should be computed

Path 4 test case Inputs Expected results: Value (i) = valid input, i < 100 Value (k) < minimum where k<i Expected results: correct average based on k values and correct totals should be computed

Path 5 test case Inputs Expected results: Value (i) = valid input where i< 100 Value (i)> maximum where k i Expected results: correct average based on n values and correct totals should be computed

Path 6 test case Inputs Expected results: Value (i) = valid input where i< 100 Expected results: correct average based on n values and correct totals should be computed

Main tactics on path selection A sufficient number of paths to achieve coverage Selection of short, functionally sensible paths Minimizing the number of changes from path to path (one decision changing at a time) Favor more but simpler paths over fewer but complicated paths

Effectiveness path testing Approximately between 60-70% of all bugs can be caught in unit testing using basis path testing

Main Limitations of Basis path testing Can not be used to show totally wrong or missing functions Interface errors may not be caught Database errors may not be caught Not all initialization errors are caught by path testing

Graph Metrices A tabular representation of flow graph with link weight addition to provide information about control flow A square matrix whose size ( row & column) is equal to the number of node on flow graph Existing connection ( 1 & 0)

Link Weight Probability an edge will be executed Processing time expended, Memory required, Resources required, during traversal of a link

Control Structure Testing Condition Testing a test case design method that exercise the logical conditions contained in a program module Data Flow Testing a method to select a test path of a program according to the location of definitions and uses of variable in the program Loop Testing a white box testing technique that focuses exclusively on the validity of loop construct

Loop Testing 4 different classes of loop : Simple loop Nested loop Concatenated loop Unstructured loop

Simple Loop test criteria The following set of test can be applied to a simple loop of size max Skip the loop entirely One pass through the loop Two passes through the loop before existing M passes through the loop where M < max max-1, max, max+1 passes through the loop

Nested Loop test criteria Start at the inner loop. Set all other loop to a minimum value Conduct simple loop testing for the innermost loop Work outward, repeat for all loops. Keeping all other outer loops at minimum value & other nested loops to “typical value” Continue until all loops tested

Concatenated Loops If independent loops, use simple loop testing If dependent, treat as nested loops

Unstructured Loops Don’t test - redesign