Software Testing

Software Testing • Component testing • Testing of individual program components • Usually responsibility of developer • Tests derived from developer’s experience • Integration testing • Testing of groups of components integrated to create system or sub-system • Responsibility of independent testing team • Tests based on a system specification Ch20 - Software Testing I

Defect Testing • Goal:to expose latent system faults • Test cannot guarantee absence of faults • Exhaustive testing impractical • Successful defect test: • one which causes system to misbehave •  finds a fault Ch20 - Software Testing I

Defect Testing Process Ch20 - Software Testing I

Black-box Testing • Tests based on inputs, expected outputs • Developed from specification, not implementation • How to select good test inputs? • Domain knowledge • Equivalence partitioning Ch20 - Software Testing I

Equivalence Partitioning • Divide inputs into equivalenceclasses, apply test cases from each class • Typical value (e.g. midpoint) • Boundary conditions • Kinds of equivalence classes • Valid/invalid inputs • Inputs for which system behave similarly • No need to test with incorrect arg types Ch20 - Software Testing I

Equivalence PartitioningExample • Function to determine abs • Function to determine sin • Four quadrants: 0°-90°, 90°-180°, 180°-270°, 270°-360° • Searching for removing an element value from a list Ch20 - Software Testing I

Remove routine specification procedure Remove (Key : ELEM ; T: ELEM_ARRAY; Found : in out BOOLEAN; L: in out ELEM_INDEX) ; Pre-condition -- the array has at least one element T’FIRST <= T’LAST Post-condition -- the element is not present in the sequence ( not Found and not (exists i, T’FIRST >= i <= T’LAST, T (i) = Key )) Ch20 - Software Testing I

Remove routine - input partitions • Inputs which conform to the pre-conditions • Inputs where a pre-condition does not hold • Inputs where the key element is a member of the array • Inputs where the key element is not a member of the array Ch20 - Software Testing I

Testing guidelines (sequences) • Test software with sequence length = 1 • with sequence length = 0 • with sequence length >> 0 • Different-length sequences • “Tickle” the first, middle and last elements of the sequence Ch20 - Software Testing I

White-box (Structural) Testing • Derive tests from study of implementation • Goal is to exercise all independent program paths (every statement) • not all dynamic paths through the program (not feasible) • Stronger, hard to do manually for complex programs • Dynamic program analyser can check paths have been executed Ch20 - Software Testing I

Program flow graphs • Each basic block is a node • Each branch is shown as a separate path; loops are drawn as arrows looping back to the loop condition node • Cyclomatic complexity = Number of edges - Number of nodes +2 Ch20 - Software Testing I

Program flow graphsExample bool Remove(int key, intarray& array) { int origSize = array.size(); for (int i = 0; i < array.size(); i++) { while (array[i] == key) { int limit = array.size(); for (int j = i; (j+1) < limit; j++) { array[j] = array[j+1]; } array.shrink(-1); } } return (array.size < origSize); } Ch20 - Software Testing I

Program flow graphsExample bool Remove(int key, intarray& array) { int origSize = array.size(); for (int i = 0; i < array.size(); i++) { while (array[i] == key) { int limit = array.size(); for (int j = i; (j+1) < limit; j++) { array[j] = array[j+1]; } array.shrink(-1); } } return (array.size < origSize); } A B C D E F G H I Ch20 - Software Testing I

Program flow graphsExample END START A B I H C D F E G Ch20 - Software Testing I

Program flow graphsExample • Cyclomatic Complexity = 11 – 9 + 2 = 4 • Therefore, 4 Traces • A, B, C, D, E, G, H, I • Array with no key in any slots • A, B, C, D, E, F, G, H, I • Array with key in some slots (but not just last slot) • A, B, I • Array of zero length • A, B, C, G, H, I • Array with key just in last slot Ch20 - Software Testing I

Software Testing