Estimation Techniques

31
Jan

Project Estimation Techniques

If you want to be successful in Project Test Estimation then you should have execution knowledge which is eventually very significant in Software Testing Life Cycle. Software Test Estimation Techniques are indeed essential to make good reputation with your client when you bid for testing projects. It also gives you idea that how your approach should be during the execution of the project.

In case, you have experience in various software testing life cycle then chances are higher that you estimate your project very well as your experience may help you in providing various ideas & techniques for that testing project. It is practically not possible to put some number of days or estimate with old time formula of one third of the development effort. The requirement keeps on changing from client side & we have to adjust the same accordingly. Some companies which offer testing services use this formula which isn’t correct as it is not based on any scientific techniques or principles.

Following factors are indeed essential for any software test estimation and they are highly recommended in any software testing organization.

  • Team Knowledge on the subject/skills
  • Historical data for the previous estimation for improvement and accuracy
  • Domain Knowledge and core requirements
  • Risks and complexity of the application
  • Team Knowledge on the subject/skills
  • Bug cycles for the project
  • Estimation should include buffer time
  • Resources availability (Like vacations, holidays, and sick days can have a great impact on your estimates)
  • Bug cycles for the project

Many techniques are used in recent years that have been developed for test estimation of the software.

Some of the Estimation Techniques are:

 Following are the popular Test Estimation Techniques:-

Use – Case Point Method:

Use-Case Point Method is completely based on the use cases that we calculate the un-adjusted actor weights to determine the software test estimation.

Use case is a document which well specifies systems, different users or other stakeholders that interact with the concerned application. They are certainly named as ‘Actors’. The interactions achieve some defined goals hence protecting the interest of all stakeholders via flow termed or different behavior as scenarios. 

The formula used for this technique is:

  • Unadjusted actor weights = total no. of actors (positive, negative and exceptional)
  • Unadjusted use case weight = total no. of use cases.
  • Unadjusted use case point = Unadjusted actor weights + Unadjusted use case weight
  • Determine the technical/environmental factor (TEF) ( if not available take as 0.50)
  • Adjusted use case point = Unadjusted use case point * [0.65+ (0.01 * TEF]
  • Total Effort = Adjusted use case point * 2

3-Point Software Testing Estimation Technique:

3-Point Software Testing Estimation Technique is completely based on statistical methods where each testing task is broken down into sub tasks and further into three types on each tasks.

The formula used by this technique is:

Test Estimate = P + (4*N) + E / 6

Whereas P = Positive Scenarios or Optimistic Estimate (Best case scenario in which nothing goes wrong and all conditions are optimal.)

N = Negative Scenarios or Most Likely Estimate (most likely duration and there may be some problem but most of the things will go right.)

E = Exceptional Scenarios or Pessimistic Estimate (worst case scenario which everything goes wrong.)

Standard deviation for the technique is calculated as,

Standard Deviation (SD) = (N – E)/6

Work Breakdown Structure:

This method is created by breaking down the test project into small pieces. Modules are separated into sub-modules. Sub modules are then further separated into functionalities and functionalities are then separated in sub-functionalities.

You should review all the requirements from Requirement Document so as to make sure that they are added in WBS. Later, figure out the number of tasks your team needs to complete. Estimate properly the duration of each task.

Wideband Delphi Estimation Technique:

Following the same procedure as above in WBS. In this, work breakdown structure is disintegrated for each task and further distributed to a team comprising of say 3-7 members so as to re-estimate the task. The final estimate is the consequence of the brief estimates that are based on the team consensus. This method actually speaks more on experience instead of any statistical formula. Moreover, this method is initially popularized by Barry Boehm to emphasize on the group iteration so as to reach to a consensus where the team visualize on the different aspects of problems whereas estimating the test effort.

Function Point/Testing Point Analysis:

The Function Point technique is a direct pointer of the functionality of software application from the user’s viewpoint. This technique is the most accepted technique that is used to estimate the size of a software project. 

This technique is also a part of TMap. In function point technique, function points are converted into test points. In Test Point analysis, we carry out following:

  • Static Test Points
  • Dynamic Test Points
  • Environmental Factor
  • Control Factor
  • Productivity Factor
  • Primary Test Hours
  • Total Test Hours
  • Control Factors

In Software Testing, estimation is generally based on previously created application prototype or requirement specification document. To calculate FP for a project, some of the major components are required.  

The major components required are:

Unadjusted Data Function Points:

  1. Internal Files
  2. External Interfaces 

Unadjusted Transaction Function Points:

  1. User Inputs
  2. User Outputs & User Inquiries

Capers Jones basic formula: 

Number of Test cases = [Number of Function Points] x 1.2

Total Actual Effort, TAE = (Number of Test cases) * (Percentage of development effort /100) 

This method is used when requirement document or a detailed low level design document is available. Previous data for development and testing & measure of function point is available.

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