The workplace I am currently in also don’t have any prescribed tools for capturing test cases. We work using Agile and use Jira for our user stories to work on.
I document my test cases using a format similar to this as a comment on each story I am testing:
The prefix describes the witnessed behaviour before the new code is deployed and the postfix describes the behaviour afterwards
Testing Result:
Pre-Fix:
Environment: [Environment-name]
Scenario 1: [Description of the test scenario]
Process:
[Bullet point list of the steps to perform the test]
Result:
[Bullet point list of the results witnessed running the process]
Scenario 2: …
Scenario 3: …
Post-Fix:
Environment: [Environment-name]
Scenario 1: [Description of the test scenario]
Process:
[Bullet point list of the steps to perform the test]
Result:
[Bullet point list of the results witnessed running the process]