feat: request/response interceptors for remote config fetch (#4484)

test/core/plugins/configs/actions.js

@@ -0,0 +1,84 @@
+/* eslint-env mocha */
+import expect, { createSpy } from "expect"
+import { downloadConfig } from "corePlugins/configs/spec-actions"
+
+describe("configs plugin - actions", () => {
+
+  describe("downloadConfig", () => {
+    it("should call the system fetch helper with a provided url", () => {
+      const fetchSpy = createSpy(async () => {}).andCallThrough()
+      const system = {
+        fn: {
+          fetch: fetchSpy
+        },
+        getConfigs() {
+          return {}
+        }
+      }
+
+      const url = "http://swagger.io/one"
+
+      downloadConfig(url)(system)
+
+      expect(fetchSpy).toHaveBeenCalledWith({
+        url: url
+      })
+    })
+    it("should allow the globally configured requestInterceptor to modify the request", () => {
+      const fetchSpy = createSpy(async () => {}).andCallThrough()
+      const requestInterceptorSpy = createSpy((req) => {
+        req.url = "http://swagger.io/two"
+        return req
+      }).andCallThrough()
+      const system = {
+        fn: {
+          fetch: fetchSpy
+        },
+        getConfigs() {
+          return {
+            requestInterceptor: requestInterceptorSpy
+          }
+        }
+      }
+
+      const url = "http://swagger.io/one"
+
+      downloadConfig(url)(system)
+
+      expect(fetchSpy).toHaveBeenCalledWith({
+        url: "http://swagger.io/two"
+      })
+    })
+    it("should allow the globally configured responseInterceptor to modify the response", async () => {
+      const fetchSpy = createSpy(async (req) => {
+        return {
+          url: req.url,
+          ok: true
+        }
+      }).andCallThrough()
+      const responseInterceptorSpy = createSpy((res) => {
+        res.url = "http://swagger.io/two"
+        return res
+      }).andCallThrough()
+      const system = {
+        fn: {
+          fetch: fetchSpy
+        },
+        getConfigs() {
+          return {
+            responseInterceptor: responseInterceptorSpy
+          }
+        }
+      }
+
+      const url = "http://swagger.io/one"
+
+      const res = await downloadConfig(url)(system)
+
+      expect(res).toEqual({
+        url: "http://swagger.io/two",
+        ok: true
+      })
+    })
+  })
+})