feat: migrate unit tests to Jest (#6353)

* config(jest): updated setup
* config(jest): update testMatch to include jsx files
* config(jest): add transformIgnorePatterns
* config(jest): update ignore files that do not work in jest yet
* config: add test:unit-jest to test script

* fix(jest): lint with eslint-plugin-jest

* refactor(jest): move unit test directory
* refactor(mocha): restore mocha tests that fail in jest

* docs(jest): update helpful scripts with test:unit-jest

test/unit/core/plugins/configs/actions.js

@@ -0,0 +1,26 @@
+
+import { downloadConfig } from "corePlugins/configs/spec-actions"
+
+describe("configs plugin - actions", () => {
+
+  describe("downloadConfig", () => {
+    it("should call the system fetch helper with a provided request", () => {
+      const fetchSpy = jest.fn(async () => {})
+      const system = {
+        fn: {
+          fetch: fetchSpy
+        }
+      }
+
+      const req = {
+        url: "http://swagger.io/one",
+        requestInterceptor: a => a,
+        responseInterceptor: a => a,
+      }
+
+      downloadConfig(req)(system)
+
+      expect(fetchSpy).toHaveBeenCalledWith(req)
+    })
+  })
+})