Getting error when running Jest tests with sfdx project at version 48

You need to update your sfdx-lwc-jest node dependency to a more recent version:

1. Edit package.json
2. Update the version of sfdx-lwc-jest under devDependencies. FYI: 0.7.0 is the latest for api v48.0 at time of writing.
3. Run npm install or yarn install depending on your Node package manager.