Postman automation test in same request

I am new to postman and I'm trying to understand how the api automation can be done using postman.

Scenario: Say, I am testing login api. For that I have following test cases.

1. Valid login (valid username and password)
2. Invalid login (wrong password)
3. Invalid login (mandatory username and password) etc My question is : for each of these test cases, should I create the requests separately and one test in each request or is there a way I can send different input values and based on each input value, I can write the appropriate test?

Any suggestions will be highly appreciated.