Black Box Testing: Black box testing focuses on testing the function of the program or application against its specifications. Specifically, this technique determines whether combinations of inputs and operations produce expected results. When creating black box test cases, the input data used is critical. Three successful techniques for managing the amount of input data required include:
Equivalence Partitioning - an equivalence class is a subset of data that is representative of large class. Equivalence partitioning is a technique for testing equivalence classes rather than undertaking exhaustive testing of each of the larger class. For example, a program which edits credit limits within a given range (10000 – 15,000) would have three equivalence classes:
o Less than 10,000 (invalid)
o Between 10,000 and 15,000 (valid)
o Greater than 15,000 (invalid)
Boundary Analysis – a technique that consists of developing test cases and data that focus on the input and output boundaries of a given function. In same credit limit example, boundary analysis would test:
o Low boundary plus or minus one (9,999 and 10,001)
o On the boundary (10,000 and 15,000)
o Upper boundary plus or minus one (14,999 and 15,001)
Error Guessing – based on the theory that test cases can be developed based upon the intuition and experience of the test engineer. For example, in an example where one of the inputs is the date, a test engineer may try February 29, 2000 or 9/9/99.