Fresh install: tests not working

[Maartenvm]

$ npm start

kt-app@0.1.0 start C:\Users\Maarten\workspace\kt-app
react-scripts start

Starting the development server...

[at-loader] Using typescript@2.2.0 from typescript and "tsconfig.json" from C:\Users\Maarten\workspace\kt-app\tsconfig.json.

[at-loader] Checking started in a separate process...

[at-loader] Checking finished with 1 errors
Failed to compile.

Error in [at-loader] ./src/App.test.tsx:6:1
TS2304: Cannot find name 'it'.

[sverhoeven]

Problem seems to only occur on Windows. On Linux and OSX this does not happen.

Workaround add import 'jest'; to src/App.test.tsx

This could have been noticed earlier by CI builds on Windows see #61