In one team (a project with multiple sprints) I was on - we started the Test strategy doc in Sprint 1, and then slowly build it from there. The test strategy doc was all the things that where equal across sprints:
- Environments
- Tools
- Approach to test automation
- Definition of Done, Definition of Ready, 3 amigos
- Delivery pipeline
That worked quite well, and improvements to the doc & test process went to the backlog along with other work products. Until it didn’t add value. DoR never got implemented, so nothing is perfect…
With that - and if you really really need a (pr sprint/pr. release) test plan the content of the test plan comes down to Requirement Scope, Test Scope and People. With the right tool this can be automatically pulled. - as mentioned here: