An usecase are prepared from BRS.this will be in document 
form only which can be understand by the team.it describe 
about how the software should when the end user uses .
where as testcases are written by tester using SRS.testcase 
are used for testing the functionality or behavior of the 
application

Actually Test cases are derived from use cases

use cases contains field validation of fields

Possitive and negative scenarios for each each functionality

Difference between test case and use case contains only 
validations but the test case contains test data

test case:it is developed by test enganeer.it is document 
level testing.it is simply understanding covering the more 
functionaity in a single shot.

use case:An usecase are prepared from BRS.this will be in 
document form only which can be understand by the team.it 
describe about how the software should when the end user 
uses .where as testcases are written by tester using SRS

Test Case: It is single whole oriented interactions 

performed by the user or tool on AUT(Application Under Test)

                     Whereas

Use Case: It depicts relationship between actor input and 

system response.