Impact from users view due to sources of defects:

• The users are the main point for the success/failure of the software product.

• If we meet their requirements our software may look like a huge success converse is also the same.

• This may result in the poor quality of software.

• And user dissatisfaction.

• Testers goal is to discover these defects preferably before the software is in operation.

• One of the ways we do this is by designing test cases that have a high probability of revealing defects.

How do we develop the test cases?

• The software testing is an experimental activity.

• The results of the test experiment are analyzed to determine the behavior of the software whether we get the desired behavior of the software or not.

• In this experimental activity a tester must develop a hypothesis .

• Based on the hypothesis he designs the test cases.

• The test cases are designed and the results are analyzed to prove the  hypothesis or disprove the hypothesis.

• Based on these hypotheses we might find some defects in the software.