The minimum requirement to start testing:-
   Build.
   Test envirnoment.
   Test Case.

The minimum requirements to start testing are
1).Test cases should be prepared and reviewed.
2).Testing environment should be ready.
3).Build should be released

Hi i am ashok from Perot Systems,
The Following are the Minimam Reqqirement to start testing
1. Receive build from development team
2. Reviewed testcases design document
3. Requirements of the customer

Following listed points should have been completed in order 
to say go for testing:
1)Build has been received from development team & 
configuration team has deployed it on QA box.

2)Test environment setup completed & test bed is prepared.

3)Tester has done his analysis on the clients requirement & 
specification.

4)Test cases are reviewed completely.

Requirements documents
Test environment
Build
Test Plan

Here test cases are not THE essential elements to start
testing compared to the above mentioned items. In some cases
testing is done on the fly and at times some of the test
cases are even written after the initial build is given. A
tester can even perform ad-hoc testing to get a feel of the
application.