When SRS is handed to Test engineers, they write test cases for each point of the SRS, What these test cases are called?

Ans: That test case called Positive test case..

if you are test the project beyond the limit/below the limit, or  test the project opposite the client requirement...then it called Negative test/ test cases.

e.g. if your 'Login' text box limit is alphanumeric 1-10

Positive test: put the number between 1-10 with alphanumeric.

Negative test: Put the number below 1(Zero) or max 10(11, 12 ...), put the character special character value