fetch plugin test: minor indentation fix

__tests__/plugins/fetch.test.js

@@ -2,13 +2,13 @@ const makeServiceWorkerEnv = require('service-worker-mock');
 
 global.fetch = require('node-fetch');
 jest.mock('node-fetch', () => {
-    const context = {
-        then: jest.fn().mockImplementationOnce(() => {
-        const response = { test: "success" };
-        return Promise.resolve(response);
-        })
-    };
-    return jest.fn(() => context);
+  const context = {
+    then: jest.fn().mockImplementation(() => {
+      const response = { test: "success" };
+      return Promise.resolve(response);
+    })
+  };
+  return jest.fn(() => context);
 });
 
 describe("plugin: fetch", () => {
@@ -34,6 +34,7 @@ describe("plugin: fetch", () => {
     require("../../plugins/fetch.js");
 
     const returnedJSON = await self.LibResilientPlugins[0].fetch('https://resilient.is/test.json');
+    expect(fetch).toHaveBeenCalled();
     expect(returnedJSON).toEqual({test: "success"})
   });
 });