Testing Estimation Question:

There are three main elements which determine estimates for black box testing: size, test strategy, and productivity. Using all three elements we can determine the estimate for black box testing for a given project. Let's take a look at these elements.

Size: The most important aspect of estimating is definitely the size of the project. The size of a project is mainly defined by the number of function points. But a function point fails or pays the least attention to the following factors:
Complexity: Complexity defines how many conditions exist in function points identified during a project. More conditions means more test cases which means more testing estimates. Software Testing Image
Interfacing: How much does one function affect the other part of the system? If a function is modified then accordingly the other systems have to be tested as one function always impacts another.
Uniformity: How reusable is the application? It is important to consider how many similar structured functions exist in the system. It is important to consider the extent to which the system allows testing with slight modifications.

Test strategy: Every project has certain requirements. The importance of all these requirements also affects testing estimates. Any requirement importance is from two perspectives: one is the user importance and the other is the user usage. Depending on these two characteristics a requirement rating can be generated and a strategy can be chalked out accordingly, which also means that estimates vary accordingly.
Productivity: This is one more important aspect to be considered while estimating black box testing. Productivity depends on many aspects.