The testing part of the development process involves systematically inputting different values to the program to check that the output matches the intended design.
If an agile development methodology has been used then each module can be tested in isolation, otherwise the testing plan will have to cover all possible combinations of inputs for all parts of the process.
Remember the boundaries identified in the Analysis part of the process? These will form most of your test plan. Testing values are split into three categories:
- Normal – Normal values cover any value that is within the boundaries.
- Extreme – Extreme values are those on the boundaries.
- Exceptional – Exceptional values are those that are not within the boundaries.
Not all types of input can be split into all three categories. For example, simply checking that text has been entered can only be normal (yes, there is text), or exceptional (no, nothing has been entered). Whereas checking the length of a string entered is less than 10 characters long can be all three. 10 is exceptional as it is beyond the allowed range. 9 is extreme as it is the last value that should be accepted. And under 9 is normal.
Example
In our program above we prompt the user to enter a value between 1 and 999.
- The normal values are 2 – 998
- The extreme values are 1 and 999
- The exceptional values are anything else e.g. 0, 1000, John, -5, 123456543
The test plan should test a range of normal values, all extreme values, and a range of different exceptional values. The plan should list the expected result, the observed result, and any feedback to be used for correcting errors in the program based on the testing. The test plan should be numbered and dated so that the results can be referred to in the evaluation stage and included as part of the deliverables listed in the scope document.
