describe is not defined when installing jest

Add following line in .eslintrc.js file

"env": {
    "jest": true
}

or

{
  "plugins": ["jest"]
},
"env": {
  "jest/globals": true
}

For more details check here, it also define the same.

Hope you installed eslint-plugin-jest package.If not kindly go through for
Documentation.

All the configuration details of Configuring ESLint.