Answer by Semih Özden for Using Jest and Cypress with Typescript causes Assertion and JestMatchers Errors

While using Cypress@10.0.3 with Jest, we are facing typescript errors. There are solutions for that.

Jest and Cypress are using same libraries so this can cause typescript problems in test files in Jest while writing unit tests.

To solve this problem we need two tsconfig.json files. One is for root tsconfig.json and the another one for ./cypress/tsconfig.json

In the root tsconfig.json file be sure that you excluded cypress and cypress.config.ts file.Also in the root tsconfig.json file be sure that add types: "types": ["jest", "@types/testing-library__jest-dom"].Please investigate root tsconfig.json file.tsconfig.json

"compilerOptions": {        ....        ..."types": ["jest", "@types/testing-library__jest-dom"],    },"include": ["next-env.d.ts", "**/*.ts", "**/*.tsx", "next-additional.d.ts"],"exclude": ["node_modules", "cypress", "__mocks__", "/email-server", "cypress.config.ts"]}

In the ./cypress/tsconfig.json file, be sure that you extended root tsconfig.json file and you add cypress.config.ts to file.Also you need to be sure that you do not exclude cypress in .cypress/tsconfig.json file.Please investigate following ./cypress/tsconfig.json file.

./cypress/tsconfig.json

"extends": "../tsconfig.json","compilerOptions": {"types": ["cypress"]    },"include": ["../node_modules/cypress","./**/*.ts","../cypress.config.ts"],"exclude": []}

This is the last update you need to follow;In the root project folder you should create jest.d.ts file to add some type definitions which Jest does not provide somehow while working with cypress.If you do not provide this file you can get JestMatchers ts errors.

jest.d.ts file

    namespace jest {        interface Matchers<R> {            toWorkProperly(a: number): R;        }    }}export {};

Note: If your project's cypress version less than cypress@10 you need to first upgrade cypress version to cypress@10.0.3 by following default cypress migration suggestions.