When to write the test specification

[socaroka]

I'm currently engaged in a hot debate regarding when is the most appropriate time in a software development project to draft the proposed test specification. I say it should be 'drafted' alongside the requirements specification - ie. at the same time as the technical spec., functional spec., etc. etc.
Working on a new user interface for a car accessories firm.

[techgnome]

It starts during the design phase. As soon as the Use Cases are built, the test specs can be started. They should be developed concurrently and independently with the design. In addition, they should be written implementation agnostic. Meaning the steps laid out shouldn't care if the entry is a text box or a date time picker. The test spec should read "Enter such and such date into the XYZ Date field."

I also believe that while the design and test specs should be created independantly, the two should work together to make sure that changes by one is reflected by the other (what happens if the designer decided to lock down the XYZ Date Field and simply populate it with the current date? The above test fails.)

Once those are done and handed off to the developer (I've found having the test cases helps to proactively test the development, it helps to see what will work and what won't and why) then the detailed test scripts/documents can be created, and should be kept from the developer - that's testing's Ace in the hole to determine if itwill pass or not.

-tg