This post will describe how I test in project that uses scrum. Tool is Jira and context is early development phase.
We have in JIRA workflow QA phase.
Frontend has code reviews and developers are able to test (there is no automation) what they code using browser.
Here is how I test in described context.
Feature is usable when user can do main flow described in jira card, for example, create business object.
I use browser and Chrome developer tools. Cards have some story description, so I ask for clarification in card comment section. Also, I observe pull request (angular framework) to see which modules changed. I am looking for feature side effects, when pull request contains changes not directly related to the card.
I approve card when feature is usable. Remember that context is early development phase, and scrum is iterative process, so there is no point to stop the feature if it is usable. For found issues or missing features, I create new card and bug or task, and I connect those two cards.
In BBST foundations lecture 2, you can learn how your testing differs depending on your context.