1. Domain Testing
Functional testing which tests the application by giving inputs and evaluating its appropriate outputs.
system does not accept invalid and out of range input values.
The main goal of the Domain testing is to check whether the system accepts the input within the acceptable range and delivers the required output.
Also, it verifies the system should not accept the inputs, conditions and indices outside the specified or valid range.
Domain testing is different from domain specific knowledge you need to test a software system.

2. Practice of domain testing
Involves testing of any one input variable or combination of
input var
Boundary testing 
Equivalence Class testing 
Only to tests of input variables
Only when tested at the system level
Only when tested one at a time
Only when tested in a very superficial way

3. Variable
Valid Class Equivalence Class
Invalid Class Equivalence Class
Boundaries & Special cases
Notes X
0-100
100
<0 -1
>100
101