http://flic.kr/p/ohtmj Whitebox Testing

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Recall: Common approaches for choosing test cases Blackbox testing: Choose based on module’s possible inputs and outputs Do not use code Often test boundary cases White-box testing: Uses internal logic to choose tests Different levels of code coverage Aka glass box testing, clear box testing Regression testing: Keep tests that reveal old bugs Rationale: “Fixed” bugs come back!

Criteria for choosing test cases: Coverage Measures Degree to which the source code of a program is tested by a test suite Examples: Statement coverage Condition coverage Path coverage Some examples will clarify, but first…

Control Flow Graphs – Frequently used to calculate coverage int foo(int x, int y) { int z = 0; if ((x>0) && (y>0)) { z = x; } return z; Basic blocks: straight-line pieces of code without any jumps or jump targets return z; z = x; int z = 0; if ((x>0) && (y>0)) { true false Jumps: control branches

Statement Coverage Set of test cases such that… Each program statement (line or basic block) is executed at least once

Define a test suite that provides statement coverage for this code return z; z = x; int z = 0; if ((x>0) && (y>0)) { true false Control Flow Graph int foo(int x, int y) { int z = 0; if ((x>0) && (y>0)) { z = x; } return z; ✔ ✔ input expected x y ✔ 1

Now try this code… Control Flow Graph F T T F T F public int bar(int x) { int result=0; if (x < 69) { if (x % 2 == 0) { result = x/2; } else { result = x*2; } } else if (x > 6969) { x = 69; x = 6969; return result; Control Flow Graph int result=0; result = x*2; F T x < 69 x % 2 == 0 T F result = x/2; T x > 6969 x = 69; F return result; x = 6969;

✔ ✔ ✔ ✔ ✔ ✔ ✔ ✔ ✔ Now try this code… Input (x) expected 1 2 2 1 6970 Control Flow Graph 70 6969 ✔ ✔ int result=0; result = x*2; ✔ ✔ F T x < 69 x % 2 == 0 T ✔ F result = x/2; ✔ ✔ T x > 6969 x = 69; ✔ F return result; ✔ x = 6969;

Condition Coverage Set of test cases such that… Each boolean expression (in control structures) evaluates to true at least once and to false at least once

✔ ✔ Define a test suite that provides condition coverage for this code return z; z = x; int z = 0; if ((x>0) && (y>0)) { true false Control Flow Graph int foo(int x, int y) { int z = 0; if ((x>0) && (y>0)) { z = x; } return z; ✔ ✔ input expected x y 1

Now try this code… Control Flow Graph F T T F T F public int bar(int x) { int result=0; if (x < 69) { if (x % 2 == 0) { result = x/2; } else { result = x*2; } } else if (x > 6969) { x = 69; x = 6969; return result; Control Flow Graph int result=0; result = x*2; F T x < 69 x % 2 == 0 T F result = x/2; T x > 6969 x = 69; F return result; x = 6969;

✔ ✔ ✔ ✔ ✔ ✔ Now try this code… Input (x) expected 1 2 2 1 6970 69 Control Flow Graph 70 6969 int result=0; result = x*2; ✔ ✔ F T x < 69 x % 2 == 0 ✔ T ✔ F result = x/2; ✔ T x > 6969 x = 69; ✔ F return result; x = 6969;

Path Coverage Set of test cases such that… Each possible path through a program’s control flow graph is taken at least once

✔ ✔ Define a test suite that provides path coverage for this code return z; z = x; int z = 0; if ((x>0) && (y>0)) { true false Control Flow Graph int foo(int x, int y) { int z = 0; if ((x>0) && (y>0)) { z = x; } return z; (a) (b) (c) input expected x y 1 Paths: a , b c ✔ ✔

Now try this code… Control Flow Graph F T T F T F public int bar(int x) { int result=0; if (x < 69) { if (x % 2 == 0) { result = x/2; } else { result = x*2; } } else if (x > 6969) { x = 69; x = 6969; return result; Control Flow Graph int result=0; result = x*2; F T x < 69 x % 2 == 0 T F result = x/2; T x > 6969 x = 69; F return result; x = 6969;

✔ ✔ ✔ ✔ Now try this code… Input (x) expected 1 2 2 1 6970 69 70 6969 Control Flow Graph int result=0; (a) (b) (c) (d) (f) (e) (g) (h) (i) (j) (k) result = x*2; F T x < 69 Paths: a , d , f , h a , d , g , i a , b , e , j a , b , c , k x % 2 == 0 ✔ T ✔ F result = x/2; ✔ ✔ T x > 6969 x = 69; F return result; x = 6969;

BONUS QUESTION

Draw a control flow graph Define test suites that provide: Given this code Draw a control flow graph Define test suites that provide: Statement coverage Condition coverage Path coverage int myF(int x, int y) { while (x > 10) { x = x – 10; if (x == 10) { break; } if (y < 20 && x%2 == 0) { y = y + 20; } else { y = y – 20; return 2*x + y;

Here’s the CFG F T F T F T int myF(int x, int y) { while (x > 10) { x = x – 10; if (x == 10) { break; } if (y < 20 && x%2 == 0) { y = y + 20; } else { y = y – 20; return 2*x + y; while (x > 10) F T x = x – 10; if (x == 10) F T break; if (y < 20 && x%2 == 0) F T y = y – 20; y = y + 20; Here’s the CFG return 2*x + y;