cannot read property 'child' of undefined mount enzyme code example
Example: enzyme TypeError: Cannot read property 'child' of undefined
downgrade to this version
"react": "^16.13.1",
"react-dom": "^16.13.1",
"enzyme": "^3.11.0",
"enzyme-adapter-react-16": "^1.15.5",
"enzyme-to-json": "^3.6.1",