Introduction to Debugging? What strategies include debugging?

When the software testing is successfully done, the next step is debugging. Debugging is the process of removing the error that has been uncovered during the testing process. Debugging process starts with the execution of a test case. The results that are attained are assessed and the actual and expected values are compared. Debugging is the process that matches symptom with the cause.

In debugging process, there is a possibility of two outcomes:
- cause is found and corrected.
- cause is not found

Debugging sounds difficult and here are some reasons why it is so:
- The cause and symptom may be located remotely.
- Sometimes when some other error is corrected, the symptom disappear.
- Human error can cause a symptom.
- Timing problem can cause a symptom.
- Non errors can cause symptoms.
- Symptoms can be intermittent.
- There is a possibility that causes are distributed across different tasks running on different processors.

Debugging strategy includes finding and correcting the cause of software error by the use of three strategies:
- Brute force uses the philosophy of let the computer find the error. Memory dumps are taken, run-time traces are invoked and program is loaded with output statements.
- Backtracking is the process which starts at the site where symptom is uncovered, source code is traced backward until cause is found.
- In cause elimination, cause hypothesis is devised and data is used to prove or disprove the hypothesis. On the other hand, list of possible causes is developed and tests are conducted to eliminate each.

What are Test Case Documents and what is the general format of test cases?

The test cases will have a generic format as below:
- Test Case ID : The test case id must be unique across the application.
- Test case description : The test case description should be very brief.
- Test Prerequisite : The test pre-requisite clearly describes what should be present in the system, before the test executes.
- Test Inputs : The test input is nothing but the test data that is prepared to be fed to the system.
- Test Steps : The test steps are the step-by-step instructions on how to carry out the test.
- Expected Results : The expected results are the ones that say what the system must give as output or how the system must react based on the test steps.
- Actual results : The actual results are the ones that say outputs of the action for the given inputs or how the system reacts for the given inputs.
- Pass/Fail : If the expected and actual results are same then test id Pass otherwise Fail.

The test cases are classified into positive and negative test cases.Positive test cases are designed to prove that the system accepts the valid inputs and then process them correctly. Suitable techniques to design the positive test cases are specification derived tests. The negative test cases are designed to prove that the system rejects invalid inputs and does not process them. Suitable techniques to design the negative test cases are error guessing, boundary value analysis, internal boundary value testing and state transition testing. The test cases details must be very clearly specified, so that a new person can go through the test cases step by step and is able to execute it.
In an online shopping application, at the user interface level, the client request the web server to display the product details by giving email id and username. The web server processes the request and will give the response. For this application, we design the unit, integration and system test cases.