White Box Testing

1. White Box Testing by : Andika Bayu H

2. 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

3. Basis Path/Control Structure Testing • Proposed by Tom McCabe • 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:

4. Pseudo Code - Flow Chart • 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 • Procedure Sort

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

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

7. 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

8. 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 ?

9. 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.

10. 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.

11. 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

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

13. 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.