White Box Testing by Andika Bayu H Introduction

White Box Testing by : Andika Bayu H

Introduction White Box Testing or Glass Box Testing ◦ Test case design method that uses the control structure of the procedural design to derive test cases SW Engineer can derive test cases that ◦ guarantee that all independent paths within a module have been exercised at least once ◦ exercise all logical decisions on their true and false bounds ◦ execute all loops at their boundaries and within their operational bounds ◦ exercise internal data structures to assure their validity Why not just validate the requirement ? ◦ Logic errors and incorrect assumptions are inversely proportional to the probability that a program path will be executed ◦ We often believe that a logical path is not likely to be executed when, in fact, it may be executed on a regular basis ◦ Typographical errors are random 2

Basis Path/Control Structure Testing Proposed by Tom Mc. Cabe The basis path method enables the test case designer to derive a logical complexity measure of a procedural design and use this measure as a guide for defining a basis set of execution paths Flow Graph Notation: 3

Pseudo Code - Flow Chart Procedure Sort • Flow Chart Procedure Sort 1. do while not eof 2. Read Record 3. if record field 1 = 0 4. then process record 5. store in buffer; 6. increment counter 7. else if record field 2 = 0 8. then reset counter 9. else process record 10. store in file 11. endif 12. endif 13. enddo 4

Flow Chart - Flow Graph • Flow Chart • Flow Graph 5

Compound Logic IF a or b then procedure X else procedure Y endif 6

Cyclomatic Complexity ( V(G) ) Cyclomatic Complexity ◦ software metric that provide a quantitative measure of the logical complexity of a program] V(G) = E - N + 2 V(G) = 9 - 8 + 2 =3 • The number of regions of the flow graph correspond to the cyclomatic complexity. • V(G) = P + 1, where P is the number of predicate nodes 7

Independent Path An independent path is any path through the program that introduces at least one new set of processing statements or a new condition An independent path must move along at least one edge that has not been traversed before the path is defined path 1: 1 -13 path 2: 1 -2 -3 -7 -8 -11 -12 -1 -13 path 3: 1 -2 -3 -7 -9 -10 -11 -12 -1 -13 path 4: 1 -2 -3 -4 -5 -6 -12 -1 -13 Is the path 1 -2 -3 -4 -5 -6 -12 -1 -2 -3 -7 -8 -11 -12 -1 -13 an independent path ? 8

Deriving Test Cases Draw a corresponding flowgraph using the design or code as a foundation Determine the cyclomatic complexity of the resultant flow graph (V(g)) Determine a basis set of linearly independent paths Prepare test cases that will force execution of each path in the basis set ◦ if we have 6 independent paths, then we should have at least 6 test cases. For each test cases, we should define the input conditions and the expected result. 9

Graph Matrices Can automate derivation of flow graph and determination of a set of basis paths. Software tools to do this can use a graph matrix. Graph matrix: · is square with #sides equal to #nodes · Rows and columns correspond to the nodes · Entries correspond to the edges. Can associate a number with each edge entry. Use a value of 1 to calculate the cyclomatic complexity · For each row, sum column values and subtract 1. · Sum these totals and add 1. 10

Some other interesting link weights: · Probability that a link (edge) will be executed · Processing time for traversal of a link · Memory required during traversal of a link · Resources required during traversal of a link 11

Loop Testing Loop is fundamental to many algorithms. Loop can be defined as simple, concatenated, nested, and unstructured. 12

Loop Testing (2) To test: · Simple Loops of size n: · Skip loop entirely · Only one pass through loop · Two passes through loop · m passes through loop where m<n. · (n-1), n, and (n+1) passes through the loop. · Nested Loops · Start with inner loop. Set all other loops to minimum values. · Conduct simple loop testing on inner loop. · Work outwards · 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. 13