White Box testing is done with the code perspective. The emphasis is to ensure that each line of the code is executed atleast once.
Unit Testing: Testing performed to isolate and expose faults and failures as soon as the source code is available, regardless of the external interfaces that may be required. Often times, the detailed design and requirements documents are used as a basis to compare how and what the unit is able to perform. White and black-box testing methods are combined during unit testing.
Can derive test cases to ensure:
1. all independent paths are exercised at least once.
2. all logical decisions are exercised for both true and false paths.
3. all loops are executed at their boundaries and within operational bounds.
4. all internal data structures are exercised to ensure validity.
Why White box testing when black box testing is there to test conformance to requirements
- Logic errors and incorrect assumptions most likely to be made when coding for "special cases". Need to ensure these execution paths are tested.
- May find assumptions about execution paths incorrect, and so make design errors. White box testing can find these errors.
- Typographical errors are random. Just as likely to be on an obscure logical path as on a mainstream path.
"Bugs lurk in corners and congregate at boundaries"
White Box Testing Techniques
1. Basis Path Testing
a. Flow Graph Notation
b. Cyclomatic Complexity
c. Deriving Test Cases
d. Graph Matrices
2. Control Structure testing
a. Conditions Testing
b. Data Flow Testing
c. Loop Testing
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