As you run tests (F6) Puppetry generates and performs Jest/Puppeteer project. Puppetry receives the report from Jest and display the report.
When the test cases of the tested bundle include page/target.screenshot method the report adds thumbnails of the generated screenshots. If you click on a thumbnail the screenshots gets shown in the viewer.
Note the icons in the top right corner. You can use them to switch viewer in fullscreen mode and to close the viewer.
Alternatively you can open a screenshot with default image viewer in your hosting OS. Just hiver the thumbnail and click on Download link.
When the test cases of the bundle include performance assertions the report has button "Download performance report", which opens with external text viewer the network activity report.
If any test cases of the bundle have failing assertions the report explains the problem:
Clicking on Error details link expands the full report from Jest.