Iterative Model

An iterative lifecycle model does not attempt to start with a full specification of requirements. Instead, development begins by specifying and implementing just part of the software, which can then be reviewed in order to identify further requirements. This process is then repeated, producing a new version of the software for each cycle of the model. Consider an iterative lifecycle model which consists of repeating the following four phases in sequence:

A Requirements phase, in which the requirements for the software are gathered and analyzed. Iteration should eventually result in a requirements phase that produces a complete and final specification of requirements. - A Design phase, in which a software solution to meet the requirements is designed. This may be a new design, or an extension of an earlier design.

An Implementation and Test phase, when the software is coded, integrated and tested.

A Review phase, in which the software is evaluated, the current requirements are reviewed, and changes and additions to requirements proposed.

For each cycle of the model, a decision has to be made as to whether the software produced by the cycle will be discarded, or kept as a starting point for the next cycle (sometimes referred to as incremental prototyping). Eventually a point will be reached where the requirements are complete and the software can be delivered, or it becomes impossible to enhance the software as required, and a fresh start has to be made.

The iterative lifecycle model can be likened to producing software by successive approximation. Drawing an analogy with mathematical methods that use successive approximation to arrive at a final solution, the benefit of such methods depends on how rapidly they converge on a solution.

The key to successful use of an iterative software development lifecycle is rigorous validation of requirements, and verification (including testing) of each version of the software against those requirements within each cycle of the model. The first three phases of the example iterative model is in fact an abbreviated form of a sequential V or waterfall lifecycle model. Each cycle of the model produces software that requires testing at the unit level, for software integration, for system integration and for acceptance. As the software evolves through successive cycles, tests have to be repeated and extended to verify each version of the software.

Amit Ahuja

Test Cases

Designing Test Cases


A test case is a detailed procedure that fully tests a feature or an aspect of a feature. Whereas the test plan describes what to test, a test case describes how to perform a particular test. You need to develop a test case for each test listed in the test plan. Figure 2.10 illustrates the point at which test case design occurs in the lab development and testing process.


Test case includes:

* The purpose of the test.

* Special hardware requirements, such as a modem.

* Special software requirements, such as a tool.

* Specific setup or configuration requirements.

* A description of how to perform the test.

* The expected results or success criteria for the test.

Test cases should be written by a team member who understands the function or technology being tested, and each test case should be submitted for peer review.

Organizations take a variety of approaches to documenting test cases; these range from developing detailed, recipe-like steps to writing general descriptions. In detailed test cases, the steps describe exactly how to perform the test. In descriptive test cases, the tester decides at the time of the test how to perform the test and what data to use.

Most organizations prefer detailed test cases because determining pass or fail criteria is usually easier with this type of case. In addition, detailed test cases are reproducible and are easier to automate than descriptive test cases. This is particularly important if you plan to compare the results of tests over time, such as when you are optimizing configurations. Detailed test cases are more time-consuming to develop and maintain. On the other hand, test cases that are open to interpretation are not repeatable and can require debugging, consuming time that would be better spent on testing.

Test Case Design

Test Case ID:

It is unique number given to test case in order to be identified.

Test description:

The description if test case you are going to test.

Revision history:

Each test case has to have its revision history in order to know when and by whom it is created or modified.

Function to be tested:

The name of function to be tested.

Environment:

It tells in which environment you are testing.

Test Setup:

Anything you need to set up outside of your application for example printers, network and so on.

Test Execution:

It is detailed description of every step of execution.

Expected Results:

The description of what you expect the function to do.

Actual Results:

pass / failed

If pass - What actually happen when you run the test.

If failed - put in description of what you've observed.


Amit Ahuja

Black Box Testing

Testing not based on any knowledge of the internal design or code. Tests are based on requirements and functionality.


Amit Ahuja