Cypress e2e testing

[sgratzl]

closes #227 depends on #279

prerequisites:

• branch is up-to-date with the branch to be merged with, i.e. develop
• build is successful
• code is cleaned up and formatted
• tested with Firefox 52, Firefox 57+, Chrome 64+, MS Edge 16+

Summary

wip of using cypress to run e2e tests.

Notes

• as part of this the location of the typings have changed to /build/src
• the idea is to test close to the UMD case. So, as if one uses the builder. Thus, the bundled/compiled version of LineUp.js is used.

Local testing

Variant 1: with prebuilt LineUp

npm run compile
npm run build:prod
npm run cy:open

Variant 2: with webpack-dev-server

First shell:

npm run compile
npm start

Second shell:

npm run cy:start

[sgratzl]

local testing

npm run compile
npm run build:prod
npm run cy:open

[sgratzl]

I added a simple test for #275 we can add more tests on the fly

[thinkh]

Very nice feature! I just tested it and it works like charm.

@sgratzl How should we proceed with this PR? Should I wait for further implementation or merge it once you addressed my two minor change requests?

Notes from my test run:

I installed the npm dependencies in my Linux subsystem for Windows (WSL1) and ran npm run cy:open. I waited for a few minutes and then cancled the verification step.

> cypress open

It looks like this is your first time using Cypress: 4.3.0

  ⠋  Verifying Cypress can run /home/user/.cache/Cypress/4.3.0/Cypress

As alternative I downloaded the Cypress Desktop and loaded the LineUp repository there. Then everything worked like it should be and all tests are green.

[sgratzl]

@sgratzl How should we proceed with this PR? Should I wait for further implementation or merge it once you addressed my two minor change requests?

merge then we can start using it

[thinkh]

Sounds good!