fetch plugin test: testing the headers

__tests__/plugins/fetch.test.js

@@ -12,7 +12,9 @@ global.fetch.mockImplementation((url, init) => {
                             {
                               status: 200,
                               statusText: "OK",
-                              headers: [],
+                              headers: {
+                                'ETag': 'TestingETagHeader'
+                              },
                               url: url
                             });
           return Promise.resolve(response);
@@ -46,4 +48,18 @@ describe("plugin: fetch", () => {
     expect(await response.json()).toEqual({test: "success"})
     expect(response.url).toEqual('https://resilient.is/test.json')
   });
+  
+  test("it should set the LibResilient headers", async () => {
+    require("../../plugins/fetch.js");
+
+    const response = await self.LibResilientPlugins[0].fetch('https://resilient.is/test.json');
+    
+    expect(fetch).toHaveBeenCalled();
+    expect(await response.json()).toEqual({test: "success"})
+    expect(response.url).toEqual('https://resilient.is/test.json')
+    expect(response.headers.has('X-LibResilient-Method')).toEqual(true)
+    expect(response.headers.get('X-LibResilient-Method')).toEqual('fetch')
+    expect(response.headers.has('X-LibResilient-Etag')).toEqual(true)
+    expect(response.headers.get('X-LibResilient-ETag')).toEqual('TestingETagHeader')
+  });
 });