The UI Framework package is on a deprecation path and is actively being removed from OpenSearch Dashboards. Progress on this project can be followed in #1060.
This framework was used to build legacy layouts in Kibana 5.x and 6.x and is replaced by EUI.
Compile the CSS with yarn uiFramework:compileCss.
You can run node scripts/jest --watch to watch for changes and run the tests as you code.
You can run node scripts/jest --coverage to generate a code coverage report to see how
fully-tested the code is.
See the documentation in scripts/jest.js for more options.