Cypress test: Add option for testing without build and deploy

Sometimes, we don't want Cypress to rebuild and redeploy the application 
every time we run the tests. Instead, we build and deploy the 
application ourselves.

For those cases, we can use npm run cypress:local:testonly and Cypress 
will skip building and deployment and move directly into testing.

Author: FinnWoelm

cypress/plugins/index.js

@@ -43,6 +43,9 @@ module.exports = (on, config) => {
   on('task', {
     // Check if deployment is currently active
     isDeployed: () => {
+      if(config.env.SKIP_DEPLOY === true)
+        return true
+
       return config.activeDeployment !== null
     },
   })

package.json

@@ -26,8 +26,10 @@
   ],
   "scripts": {
     "test": "jest --config tests/jest.config.js",
-    "cypress:local": "env CYPRESS_DEPLOY=local cypress run --config-file false",
-    "cypress:netlify": "env CYPRESS_DEPLOY=netlify cypress run --config-file false"
+    "cypress:local":    "env CYPRESS_DEPLOY=local   cypress run --config-file false",
+    "cypress:netlify":  "env CYPRESS_DEPLOY=netlify cypress run --config-file false",
+    "cypress:local:testonly":   "env CYPRESS_SKIP_DEPLOY=true npm run cypress:local",
+    "cypress:netlify:testonly": "env CYPRESS_SKIP_DEPLOY=true npm run cypress:netlify"
   },
   "devDependencies": {
     "cypress": "^4.6.0",