• Educated Guesstimate
  - more difficult without previous experience of knowledge in system/application
  - make adjustments for ramp up time and the learning curve of testing personnel
  
  
• Percentage of Development Time
  - 50% - 75% - 100% - more depending on platform and development technology being used
  
  
• Work backwards to determine how much time can be spent on any given function based on the dictated test window
  
  
• Time allotted to each test case and/or features/functions/requirements
  - could use a scale of time based on simple/moderate/complex items
  - then add a pad for retest and/or just plain unexpected situations
  
  
• Estimates for future builds or releases based on actual test durations from previous builds or releases
  

Considerations, Regardless of Approach, That May Need to be Factored In:

• Previous knowledge (or lack thereof) with the application or system
  
• Maturity and/or completeness of the requirements
  
• Developer track record for quality, and experience level
  
• Complexity of design and code
  
• Development approach - e.g. object-oriented vs. non-object-oriented
  
• Technology and/or language
  
• Architecture complexity
  
• Number of interfaces
  
• Introduction of a new tool
  
  
• Experience level of the Test Analyst in testing methods and techniques
  
  
• Level(s) of testing to be included in the estimate (e.g. Unit, System, Acceptance)
  - may need or want to vary estimating factor based on the level
  
  
• What activities need to be included in the estimate, such as:
  
  - test planning? - test case design?
  
  - test execution and defect reporting? - retesting?
  
  - documentation generation? - tests within the test team and outside the test team
  
  - test environment preparation? - test tool implementation?