meta: introduce Cypress end-to-end testing (via #4827)

* `test/e2e` -> `test/e2e-selenium`

* add Cypress

* ESLint fixes

* MOAR cypress

* `integration` -> `tests`

* wire Cypress up to a hot e2e server

* linter fixes

* don't run in CI

test/e2e-selenium/scenarios/schemeContainer.js

@@ -0,0 +1,52 @@
+describe("Render scheme", function () {
+    let mainPage
+    let schemeContainer
+    beforeEach(function (client, done) {
+
+        mainPage = client
+        .url("localhost:3230")
+        .page.main()
+
+        schemeContainer = mainPage.section.schemeContainer
+
+        client.waitForElementVisible(".download-url-input:not([disabled])", 5000)
+        .pause(5000)
+        .clearValue(".download-url-input")
+        .setValue(".download-url-input", "http://localhost:3230/test-specs/petstore.json")
+        .click("button.download-url-button")
+        .pause(1000)
+
+
+        done()
+    })
+
+    it("render section", function (client) {
+        mainPage.expect.section("@schemeContainer").to.be.visible.before(5000)
+
+        client.end()
+    })
+    it("render scheme option", function (client) {
+        schemeContainer.waitForElementVisible("@httpOption", 5000)
+        .expect.element("@httpOption").to.be.selected
+
+        client.end()
+    })
+
+    it("render authorized button", function (client) {
+        schemeContainer.waitForElementVisible("@btnAuthorize", 5000)
+        .expect.element("@btnAuthorize").to.be.visible
+
+        client.end()
+    })
+    it("render click event", function(client) {
+        schemeContainer.waitForElementVisible("@btnAuthorize", 5000)
+        .click("@btnAuthorize")
+        .assert.visible("@authorizationModal")
+        .assert.containsText("@appName", "Application: your-app-name")
+        .assert.containsText("@authorizationUrl", "http://petstore.swagger.io/oauth/dialog")
+        .assert.containsText("@flow", "implicit")
+        .assert.value("@inputClientID", "your-client-id")
+
+        client.end()
+    })
+})