What are Test Case Documents and how to design good test cases?

Designing good test cases is a complex art. The complexity comes from three sources:
- Test cases help us discover information. Different types of tests are more effective for different classes of information.
- Test cases can be good in a variety of ways. No test case will be good in all of them.
- People tend to create test cases according to certain testing styles, such as domain testing or risk based testing. Good domain tests are different from good risk based tests.
A test case specifies the pretest state of the IUT and its environment, the test inputs or conditions, and the expected result. The expected result specifies what the IUT should produce from the test inputs. The specification includes messages generated by the IUT, exceptions, returned values, and resultant state of the IUT and its environment. Test cases may also specify initial and resulting conditions for other objects that constitute the IUT and its environment.

A scenario is a hypothetical story, used to help a person think through a complex problem or system.

Characteristics of Good Scenarios

A scenario test has five key characteristics:
a story that is motivating, credible, complex and easy to evaluate.The primary objective of test case design is to derive a set of tests that have the highest attitude of discovering defects in the software. Test cases are designed based on the analysis of requirements. use cases, and technical specifications, and they should be developed in parallel with the software development effort.

A test case describes a set of actions to be performed and the results that are expected. A test case should target specific functionality or aim to exercise a valid path through a use case. This should include invalid user actions and illegal inputs that are not necessarily listed in the use case. A test case is described depends on several factors, e.g. the number of test cases, the frequency with which they change, the level of automation employed, the skill of the testers, the selected testing methodology, staff turnover, and risk.