housekeeping: reorganize and rewire Mocha tests (#5600)

* move Mocha-run tests to `test/mocha`

* fix relative paths

* fix JSX test paths

* update stagnated JSX tests

* `test/setup.js` -> `test/mocha/setup.js`

* use regex+globstar for test matching

* remove `console.log`

test/mocha/bugs/3279-empty-markdown-source.jsx

@@ -0,0 +1,37 @@
+/* eslint-env mocha */
+import React from "react"
+import expect from "expect"
+import { render } from "enzyme"
+import Markdown from "components/providers/markdown"
+
+describe("UI-3279: Empty Markdown inputs causing bare `undefined` in output", function(){
+  it("should return no text for `null` as source input", function(){
+    let props = {
+      source: null
+    }
+
+    let el = render(<Markdown {...props}/>)
+
+    expect(el.text()).toEqual("")
+  })
+
+  it("should return no text for `undefined` as source input", function(){
+    let props = {
+      source: undefined
+    }
+
+    let el = render(<Markdown {...props}/>)
+
+    expect(el.text()).toEqual("")
+  })
+
+  it("should return no text for empty string as source input", function(){
+    let props = {
+      source: ""
+    }
+
+    let el = render(<Markdown {...props}/>)
+
+    expect(el.text()).toEqual("")
+  })
+})