diff --git a/README.md b/README.md
index 978462e..f63ab94 100644
--- a/README.md
+++ b/README.md
@@ -2,7 +2,7 @@
 
 Adds retry functionality to the `Fetch` API.
 
-It wraps [isomorphic-fetch](https://github.com/matthew-andrews/isomorphic-fetch) and retries requests that fail due to network issues. It can also be configured to retry requests on specific HTTP status codes.
+It wraps any `Fetch` API package (eg: [isomorphic-fetch](https://github.com/matthew-andrews/isomorphic-fetch), [cross-fetch](https://github.com/lquixada/cross-fetch), [isomorphic-unfetch](https://github.com/developit/unfetch) and etc.) and retries requests that fail due to network issues. It can also be configured to retry requests on specific HTTP status codes.
 
 [![Build Status](https://travis-ci.org/jonbern/fetch-retry.svg?branch=master)](https://travis-ci.org/jonbern/fetch-retry)
 
@@ -18,7 +18,8 @@ npm install fetch-retry --save
 These properties are optional, and when omitted will default to 3 retries, a 1000ms retry delay, and to retry only on network errors.
 
 ```javascript
-var fetch = require('fetch-retry');
+var originalFetch = require('isomorphic-fetch');
+var fetch = require('fetch-retry')(originalFetch);
 ```
 
 ```javascript
diff --git a/index.d.ts b/index.d.ts
index 575a01d..b59ddf4 100644
--- a/index.d.ts
+++ b/index.d.ts
@@ -17,6 +17,6 @@ declare module 'fetch-retry' {
     retryOn?: number[] | RequestRetryOnFunction;
   }
 
-  function fetch(url: String, options?: IRequestInitWithRetry): Promise<Response>;
-  export = fetch;
-}
+  function fetchBuilder(fetch: (url: String, options?: RequestInit) => Promise<Response>): ((url: String, options?: IRequestInitWithRetry) => Promise<Response>);
+  export = fetchBuilder;
+}
\ No newline at end of file
diff --git a/index.js b/index.js
index 301add3..ad920f2 100644
--- a/index.js
+++ b/index.js
@@ -1,81 +1,86 @@
 'use strict';
-require('isomorphic-fetch');
 require('es6-promise').polyfill();
 
-module.exports = function(url, options) {
-  var retries = 3;
-  var retryDelay = 1000;
-  var retryOn = [];
+module.exports = function (fetch) {
+  if (typeof fetch !== 'function') {
+    throw new ArgumentError('fetch must be a function');
+  }
+
+  return function fetchRetry(url, options) {
+    var retries = 3;
+    var retryDelay = 1000;
+    var retryOn = [];
 
-  if (options && options.retries !== undefined) {
-    if (isPositiveInteger(options.retries)) {
-      retries = options.retries;
-    } else {
-      throw new ArgumentError('retries must be a positive integer');
+    if (options && options.retries !== undefined) {
+      if (isPositiveInteger(options.retries)) {
+        retries = options.retries;
+      } else {
+        throw new ArgumentError('retries must be a positive integer');
+      }
     }
-  }
 
-  if (options && options.retryDelay !== undefined) {
-    if (isPositiveInteger(options.retryDelay) || (typeof options.retryDelay === 'function')) {
-      retryDelay = options.retryDelay;
-    } else {
-      throw new ArgumentError('retryDelay must be a positive integer or a function returning a positive integer');
+    if (options && options.retryDelay !== undefined) {
+      if (isPositiveInteger(options.retryDelay) || (typeof options.retryDelay === 'function')) {
+        retryDelay = options.retryDelay;
+      } else {
+        throw new ArgumentError('retryDelay must be a positive integer or a function returning a positive integer');
+      }
     }
-  }
 
-  if (options && options.retryOn) {
-    if (Array.isArray(options.retryOn) || (typeof options.retryOn === 'function')) {
-      retryOn = options.retryOn;
-    } else {
-      throw new ArgumentError('retryOn property expects an array or function');
+    if (options && options.retryOn) {
+      if (Array.isArray(options.retryOn) || (typeof options.retryOn === 'function')) {
+        retryOn = options.retryOn;
+      } else {
+        throw new ArgumentError('retryOn property expects an array or function');
+      }
     }
-  }
 
-  return new Promise(function(resolve, reject) {
-    var wrappedFetch = function(attempt) {
-      fetch(url, options)
-        .then(function(response) {
-          if (Array.isArray(retryOn) && retryOn.indexOf(response.status) === -1) {
-            resolve(response);
-          } else if (typeof retryOn === 'function') {
-            if (retryOn(attempt, null, response)) {
-              retry(attempt, null, response);
-            } else {
+    return new Promise(function (resolve, reject) {
+      var wrappedFetch = function (attempt) {
+        fetch(url, options)
+          .then(function (response) {
+            if (Array.isArray(retryOn) && retryOn.indexOf(response.status) === -1) {
               resolve(response);
-            }
-          } else {
-            if (attempt < retries) {
-              retry(attempt, null, response);
+            } else if (typeof retryOn === 'function') {
+              if (retryOn(attempt, null, response)) {
+                retry(attempt, null, response);
+              } else {
+                resolve(response);
+              }
             } else {
-              resolve(response);
+              if (attempt < retries) {
+                retry(attempt, null, response);
+              } else {
+                resolve(response);
+              }
             }
-          }
-        })
-        .catch(function(error) {
-          if (typeof retryOn === 'function') {
-            if (retryOn(attempt, error, null)) {
+          })
+          .catch(function (error) {
+            if (typeof retryOn === 'function') {
+              if (retryOn(attempt, error, null)) {
+                retry(attempt, error, null);
+              } else {
+                reject(error);
+              }
+            } else if (attempt < retries) {
               retry(attempt, error, null);
             } else {
               reject(error);
             }
-          } else if (attempt < retries) {
-            retry(attempt, error, null);
-          } else {
-            reject(error);
-          }
-        });
-    };
+          });
+      };
 
-    function retry(attempt, error, response) {
-      var delay = (typeof retryDelay === 'function') ?
-        retryDelay(attempt, error, response) : retryDelay;
-      setTimeout(function() {
-        wrappedFetch(++attempt);
-      }, delay);
-    }
+      function retry(attempt, error, response) {
+        var delay = (typeof retryDelay === 'function') ?
+          retryDelay(attempt, error, response) : retryDelay;
+        setTimeout(function () {
+          wrappedFetch(++attempt);
+        }, delay);
+      }
 
-    wrappedFetch(0);
-  });
+      wrappedFetch(0);
+    });
+  };
 };
 
 function isPositiveInteger(value) {
diff --git a/package-lock.json b/package-lock.json
index e21b830..ef90128 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -648,6 +648,7 @@
       "version": "0.1.12",
       "resolved": "https://registry.npmjs.org/encoding/-/encoding-0.1.12.tgz",
       "integrity": "sha1-U4tm8+5izRq1HsMjgp0flIDHS+s=",
+      "dev": true,
       "requires": {
         "iconv-lite": "~0.4.13"
       }
@@ -943,16 +944,6 @@
         "flat-cache": "^2.0.1"
       }
     },
-    "fill-keys": {
-      "version": "1.0.2",
-      "resolved": "https://registry.npmjs.org/fill-keys/-/fill-keys-1.0.2.tgz",
-      "integrity": "sha1-mo+jb06K1jTjv2tPPIiCVRRS6yA=",
-      "dev": true,
-      "requires": {
-        "is-object": "~1.0.1",
-        "merge-descriptors": "~1.0.0"
-      }
-    },
     "finalhandler": {
       "version": "1.1.2",
       "resolved": "https://registry.npmjs.org/finalhandler/-/finalhandler-1.1.2.tgz",
@@ -1176,9 +1167,13 @@
       }
     },
     "iconv-lite": {
-      "version": "0.4.16",
-      "resolved": "https://registry.npmjs.org/iconv-lite/-/iconv-lite-0.4.16.tgz",
-      "integrity": "sha1-Zd477rOeKWDWfwSfFjT/y83pAUs="
+      "version": "0.4.24",
+      "resolved": "https://registry.npmjs.org/iconv-lite/-/iconv-lite-0.4.24.tgz",
+      "integrity": "sha512-v3MXnZAcvnywkTUEZomIActle7RXXeedOR31wwl7VlyoXO4Qi9arvSenNQWne1TcRwhCL1HwLI21bEqdpj8/rA==",
+      "dev": true,
+      "requires": {
+        "safer-buffer": ">= 2.1.2 < 3"
+      }
     },
     "ignore": {
       "version": "4.0.6",
@@ -1272,12 +1267,6 @@
         "is-extglob": "^2.1.1"
       }
     },
-    "is-object": {
-      "version": "1.0.1",
-      "resolved": "https://registry.npmjs.org/is-object/-/is-object-1.0.1.tgz",
-      "integrity": "sha1-iVJojF7C/9awPsyF52ngKQMINHA=",
-      "dev": true
-    },
     "is-promise": {
       "version": "2.1.0",
       "resolved": "https://registry.npmjs.org/is-promise/-/is-promise-2.1.0.tgz",
@@ -1287,7 +1276,8 @@
     "is-stream": {
       "version": "1.1.0",
       "resolved": "https://registry.npmjs.org/is-stream/-/is-stream-1.1.0.tgz",
-      "integrity": "sha1-EtSj3U5o4Lec6428hBc66A2RykQ="
+      "integrity": "sha1-EtSj3U5o4Lec6428hBc66A2RykQ=",
+      "dev": true
     },
     "isarray": {
       "version": "0.0.1",
@@ -1305,6 +1295,7 @@
       "version": "2.2.1",
       "resolved": "https://registry.npmjs.org/isomorphic-fetch/-/isomorphic-fetch-2.2.1.tgz",
       "integrity": "sha1-YRrhrPFPXoH3KVB0coGf6XM1WKk=",
+      "dev": true,
       "requires": {
         "node-fetch": "^1.0.1",
         "whatwg-fetch": ">=0.10.0"
@@ -1650,12 +1641,6 @@
         "supports-color": "5.4.0"
       }
     },
-    "module-not-found-error": {
-      "version": "1.0.1",
-      "resolved": "https://registry.npmjs.org/module-not-found-error/-/module-not-found-error-1.0.1.tgz",
-      "integrity": "sha1-z4tP9PKWQGdNbN0CsOO8UjwrvcA=",
-      "dev": true
-    },
     "ms": {
       "version": "2.0.0",
       "resolved": "https://registry.npmjs.org/ms/-/ms-2.0.0.tgz",
@@ -1723,9 +1708,10 @@
       }
     },
     "node-fetch": {
-      "version": "1.6.3",
-      "resolved": "https://registry.npmjs.org/node-fetch/-/node-fetch-1.6.3.tgz",
-      "integrity": "sha1-3CNO3WSJmC1Y6PDbT2lQKavNjAQ=",
+      "version": "1.7.3",
+      "resolved": "https://registry.npmjs.org/node-fetch/-/node-fetch-1.7.3.tgz",
+      "integrity": "sha512-NhZ4CsKx7cYm2vSrBAr2PvFOe6sWDf0UYLRqA6svUYg7+/TSfVAu49jYC4BvQ4Sms9SZgdqGBgroqfDhJdTyKQ==",
+      "dev": true,
       "requires": {
         "encoding": "^0.1.11",
         "is-stream": "^1.0.1"
@@ -2014,17 +2000,6 @@
         "ipaddr.js": "1.9.0"
       }
     },
-    "proxyquire": {
-      "version": "2.1.3",
-      "resolved": "https://registry.npmjs.org/proxyquire/-/proxyquire-2.1.3.tgz",
-      "integrity": "sha512-BQWfCqYM+QINd+yawJz23tbBM40VIGXOdDw3X344KcclI/gtBbdWF6SlQ4nK/bYhF9d27KYug9WzljHC6B9Ysg==",
-      "dev": true,
-      "requires": {
-        "fill-keys": "^1.0.2",
-        "module-not-found-error": "^1.0.1",
-        "resolve": "^1.11.1"
-      }
-    },
     "pseudomap": {
       "version": "1.0.2",
       "resolved": "https://registry.npmjs.org/pseudomap/-/pseudomap-1.0.2.tgz",
@@ -2659,9 +2634,10 @@
       "dev": true
     },
     "whatwg-fetch": {
-      "version": "2.0.3",
-      "resolved": "https://registry.npmjs.org/whatwg-fetch/-/whatwg-fetch-2.0.3.tgz",
-      "integrity": "sha1-nITsLc9oGH/wC8ZOEnS0QhduHIQ="
+      "version": "3.0.0",
+      "resolved": "https://registry.npmjs.org/whatwg-fetch/-/whatwg-fetch-3.0.0.tgz",
+      "integrity": "sha512-9GSJUgz1D4MfyKU7KRqwOjXCXTqWdFNvEr7eUBYchQiVc744mqK/MzXPNR2WsPkmkOa4ywfg8C2n8h+13Bey1Q==",
+      "dev": true
     },
     "which": {
       "version": "1.3.1",
diff --git a/package.json b/package.json
index 8d28b19..0aed3be 100644
--- a/package.json
+++ b/package.json
@@ -19,8 +19,7 @@
   "author": "Jon K. Bernhardsen",
   "license": "MIT",
   "dependencies": {
-    "es6-promise": "^4.2.8",
-    "isomorphic-fetch": "^2.2.1"
+    "es6-promise": "^4.2.8"
   },
   "devDependencies": {
     "body-parser": "^1.19.0",
@@ -29,9 +28,9 @@
     "eslint": "^6.2.2",
     "expectations": "^0.7.1",
     "express": "^4.17.1",
+    "isomorphic-fetch": "^2.2.1",
     "mocha": "^5.2.0",
     "nyc": "^14.1.1",
-    "proxyquire": "^2.1.3",
     "sinon": "^6.3.5"
   }
 }
diff --git a/test/integration/index.js b/test/integration/index.js
index ddcb1bb..948e6c1 100644
--- a/test/integration/index.js
+++ b/test/integration/index.js
@@ -4,7 +4,8 @@ const chaiAsPromised = require('chai-as-promised');
 chai.use(chaiAsPromised);
 chai.should();
 const childProcess = require('child_process');
-const fetchRetry = require('../../');
+const fetch = require('isomorphic-fetch');
+const fetchRetry = require('../../')(fetch);
 
 describe('fetch-retry integration tests', () => {
 
diff --git a/test/unit/index.js b/test/unit/index.js
index 680b22d..5a3c9cf 100644
--- a/test/unit/index.js
+++ b/test/unit/index.js
@@ -1,12 +1,28 @@
 'use strict';
-require('isomorphic-fetch');
-var proxyquire = require('proxyquire').noPreserveCache();
+var fetchBuilder = require('../../');
 var sinon = require('sinon');
 var expect = require('expectations');
 var Promise = require('es6-promise');
 
-describe('fetch-retry', function() {
+describe('fetchBuilder', function () {
 
+  it('should accept fetch function as argument', function () {
+    expect(function () {
+      fetchBuilder();
+    }).toThrow({
+      name: 'ArgumentError',
+      message: 'fetch must be a function'
+    });
+  });
+
+  it('should return fetchRetry function', function () {
+    expect(typeof fetchBuilder(function () { })).toBe('function');
+  });
+});
+
+describe('fetch-retry', function () {
+
+  var fetch;
   var fetchRetry;
 
   var deferred1;
@@ -20,55 +36,51 @@ describe('fetch-retry', function() {
   var clock;
   var delay;
 
-  beforeEach(function() {
+  beforeEach(function () {
     delay = 1000;
     clock = sinon.useFakeTimers();
   });
 
-  afterEach(function() {
+  afterEach(function () {
     clock.restore();
   });
 
-  beforeEach(function() {
+  beforeEach(function () {
     deferred1 = defer();
     deferred2 = defer();
     deferred3 = defer();
     deferred4 = defer();
 
-    global.fetch = sinon.stub();
+    fetch = sinon.stub();
     fetch.onCall(0).returns(deferred1.promise);
     fetch.onCall(1).returns(deferred2.promise);
     fetch.onCall(2).returns(deferred3.promise);
     fetch.onCall(3).returns(deferred4.promise);
 
-    var stubs = {
-      'isomorphic-fetch': fetch
-    };
-
-    fetchRetry = proxyquire('../../', stubs);
+    fetchRetry = fetchBuilder(fetch);
   });
 
-  describe('#url', function() {
+  describe('#url', function () {
 
     var expectedUrl = 'http://some-url.com';
 
-    beforeEach(function() {
+    beforeEach(function () {
       fetchRetry(expectedUrl);
     });
 
-    it('passes #url to fetch', function() {
+    it('passes #url to fetch', function () {
       expect(fetch.getCall(0).args[0]).toBe(expectedUrl);
     });
 
   });
 
-  describe('#options', function() {
+  describe('#options', function () {
 
-    describe('when #options is provided', function() {
+    describe('when #options is provided', function () {
 
       var options;
 
-      beforeEach(function() {
+      beforeEach(function () {
         options = {
           retries: 3,
           whatever: 'something'
@@ -77,14 +89,14 @@ describe('fetch-retry', function() {
         fetchRetry('http://someUrl', options);
       });
 
-      it('passes options to fetch', function() {
+      it('passes options to fetch', function () {
         expect(fetch.getCall(0).args[1]).toEqual(options);
       });
 
       describe('when #options.retryOn is not an array or function', () => {
 
         it('throws exception', () => {
-          expect(function() {
+          expect(function () {
             options.retryOn = 503;
             fetchRetry('http://someUrl', options);
           }).toThrow({
@@ -97,15 +109,15 @@ describe('fetch-retry', function() {
 
     });
 
-    describe('when #options is undefined or null', function() {
+    describe('when #options is undefined or null', function () {
 
-      [undefined, null].forEach(function(testCase) {
+      [undefined, null].forEach(function (testCase) {
 
-        beforeEach(function() {
+        beforeEach(function () {
           fetchRetry('http://someUrl', testCase);
         });
 
-        it('does not pass through options to fetch', function() {
+        it('does not pass through options to fetch', function () {
           expect(fetch.getCall(0).args[1]).toEqual(undefined);
         });
 
@@ -115,11 +127,11 @@ describe('fetch-retry', function() {
 
   });
 
-  describe('#options.retries', function() {
+  describe('#options.retries', function () {
 
-    describe('when #options.retries=3 (default)', function() {
+    describe('when #options.retries=3 (default)', function () {
 
-      beforeEach(function() {
+      beforeEach(function () {
         thenCallback = sinon.spy();
         catchCallback = sinon.spy();
 
@@ -128,19 +140,19 @@ describe('fetch-retry', function() {
           .catch(catchCallback);
       });
 
-      describe('when first call is a success', function() {
+      describe('when first call is a success', function () {
 
-        beforeEach(function() {
+        beforeEach(function () {
           deferred1.resolve({ status: 200 });
         });
 
-        describe('when resolved', function() {
+        describe('when resolved', function () {
 
-          it('invokes the then callback', function() {
+          it('invokes the then callback', function () {
             expect(thenCallback.called).toBe(true);
           });
 
-          it('calls fetch once', function() {
+          it('calls fetch once', function () {
             expect(fetch.callCount).toBe(1);
           });
 
@@ -148,26 +160,26 @@ describe('fetch-retry', function() {
 
       });
 
-      describe('when first call is a failure', function() {
+      describe('when first call is a failure', function () {
 
-        beforeEach(function() {
+        beforeEach(function () {
           deferred1.reject();
         });
 
-        describe('when second call is a success', function() {
+        describe('when second call is a success', function () {
 
-          beforeEach(function() {
+          beforeEach(function () {
             clock.tick(delay);
             deferred2.resolve({ status: 200 });
           });
 
-          describe('when resolved', function() {
+          describe('when resolved', function () {
 
-            it('invokes the then callback', function() {
+            it('invokes the then callback', function () {
               expect(thenCallback.called).toBe(true);
             });
 
-            it('calls fetch twice', function() {
+            it('calls fetch twice', function () {
               expect(fetch.callCount).toBe(2);
             });
 
@@ -175,27 +187,27 @@ describe('fetch-retry', function() {
 
         });
 
-        describe('when second call is a failure', function() {
+        describe('when second call is a failure', function () {
 
-          beforeEach(function() {
+          beforeEach(function () {
             deferred2.reject();
             clock.tick(delay);
           });
 
-          describe('when third call is a success', function() {
+          describe('when third call is a success', function () {
 
-            beforeEach(function() {
+            beforeEach(function () {
               deferred3.resolve({ status: 200 });
               clock.tick(delay);
             });
 
-            describe('when resolved', function() {
+            describe('when resolved', function () {
 
-              it('invokes the then callback', function() {
+              it('invokes the then callback', function () {
                 expect(thenCallback.called).toBe(true);
               });
 
-              it('calls fetch three times', function() {
+              it('calls fetch three times', function () {
                 expect(fetch.callCount).toBe(3);
               });
 
@@ -203,27 +215,27 @@ describe('fetch-retry', function() {
 
           });
 
-          describe('when third call is a failure', function() {
+          describe('when third call is a failure', function () {
 
-            beforeEach(function() {
+            beforeEach(function () {
               deferred3.reject();
               clock.tick(delay);
             });
 
-            describe('when fourth call is a success', function() {
+            describe('when fourth call is a success', function () {
 
-              beforeEach(function() {
+              beforeEach(function () {
                 deferred4.resolve({ status: 200 });
                 clock.tick(delay);
               });
 
-              describe('when resolved', function() {
+              describe('when resolved', function () {
 
-                it('invokes the then callback', function() {
+                it('invokes the then callback', function () {
                   expect(thenCallback.called).toBe(true);
                 });
 
-                it('calls fetch four times', function() {
+                it('calls fetch four times', function () {
                   expect(fetch.callCount).toBe(4);
                 });
 
@@ -231,20 +243,20 @@ describe('fetch-retry', function() {
 
             });
 
-            describe('when fourth call is a failure', function() {
+            describe('when fourth call is a failure', function () {
 
-              beforeEach(function() {
+              beforeEach(function () {
                 deferred4.reject();
                 clock.tick(delay);
               });
 
-              describe('when rejected', function() {
+              describe('when rejected', function () {
 
-                it('invokes the catch callback', function() {
+                it('invokes the catch callback', function () {
                   expect(catchCallback.called).toBe(true);
                 });
 
-                it('does not call fetch again', function() {
+                it('does not call fetch again', function () {
                   expect(fetch.callCount).toBe(4);
                 });
 
@@ -260,9 +272,9 @@ describe('fetch-retry', function() {
 
     });
 
-    describe('when #options.retries=1', function() {
+    describe('when #options.retries=1', function () {
 
-      beforeEach(function() {
+      beforeEach(function () {
         thenCallback = sinon.spy();
         catchCallback = sinon.spy();
 
@@ -271,19 +283,19 @@ describe('fetch-retry', function() {
           .catch(catchCallback);
       });
 
-      describe('when first call is a success', function() {
+      describe('when first call is a success', function () {
 
-        beforeEach(function() {
+        beforeEach(function () {
           deferred1.resolve({ status: 200 });
         });
 
-        describe('when resolved', function() {
+        describe('when resolved', function () {
 
-          it('invokes the then callback', function() {
+          it('invokes the then callback', function () {
             expect(thenCallback.called).toBe(true);
           });
 
-          it('calls fetch once', function() {
+          it('calls fetch once', function () {
             expect(fetch.callCount).toBe(1);
           });
 
@@ -291,27 +303,27 @@ describe('fetch-retry', function() {
 
       });
 
-      describe('when first call is a failure', function() {
+      describe('when first call is a failure', function () {
 
-        beforeEach(function() {
+        beforeEach(function () {
           deferred1.reject();
           clock.tick(delay);
         });
 
-        describe('when second call is a success', function() {
+        describe('when second call is a success', function () {
 
-          beforeEach(function() {
+          beforeEach(function () {
             deferred2.resolve({ status: 200 });
             clock.tick(delay);
           });
 
-          describe('when resolved', function() {
+          describe('when resolved', function () {
 
-            it('invokes the then callback', function() {
+            it('invokes the then callback', function () {
               expect(thenCallback.called).toBe(true);
             });
 
-            it('calls fetch twice', function() {
+            it('calls fetch twice', function () {
               expect(fetch.callCount).toBe(2);
             });
 
@@ -319,20 +331,20 @@ describe('fetch-retry', function() {
 
         });
 
-        describe('when second call is a failure', function() {
+        describe('when second call is a failure', function () {
 
-          beforeEach(function() {
+          beforeEach(function () {
             deferred2.reject();
             clock.tick(delay);
           });
 
-          describe('when rejected', function() {
+          describe('when rejected', function () {
 
-            it('invokes the catch callback', function() {
+            it('invokes the catch callback', function () {
               expect(catchCallback.called).toBe(true);
             });
 
-            it('does not call fetch again', function() {
+            it('does not call fetch again', function () {
               expect(fetch.callCount).toBe(2);
             });
 
@@ -344,9 +356,9 @@ describe('fetch-retry', function() {
 
     });
 
-    describe('when #options.retries=0', function() {
+    describe('when #options.retries=0', function () {
 
-      beforeEach(function() {
+      beforeEach(function () {
         thenCallback = sinon.spy();
         catchCallback = sinon.spy();
 
@@ -355,19 +367,19 @@ describe('fetch-retry', function() {
           .catch(catchCallback);
       });
 
-      describe('when first call is a success', function() {
+      describe('when first call is a success', function () {
 
-        beforeEach(function() {
+        beforeEach(function () {
           deferred1.resolve({ status: 200 });
         });
 
-        describe('when resolved', function() {
+        describe('when resolved', function () {
 
-          it('invokes the then callback', function() {
+          it('invokes the then callback', function () {
             expect(thenCallback.called).toBe(true);
           });
 
-          it('calls fetch once', function() {
+          it('calls fetch once', function () {
             expect(fetch.callCount).toBe(1);
           });
 
@@ -375,15 +387,15 @@ describe('fetch-retry', function() {
 
       });
 
-      describe('when first call is a failure', function() {
+      describe('when first call is a failure', function () {
 
-        beforeEach(function() {
+        beforeEach(function () {
           deferred1.reject();
         });
 
         describe('when rejected', () => {
 
-          it('invokes the catch callback', function() {
+          it('invokes the catch callback', function () {
             expect(catchCallback.called).toBe(true);
           });
 
@@ -413,14 +425,14 @@ describe('fetch-retry', function() {
 
   });
 
-  describe('#options.retryDelay', function() {
+  describe('#options.retryDelay', function () {
 
-    describe('when #options.retryDelay is a number', function() {
+    describe('when #options.retryDelay is a number', function () {
 
       var options;
       var retryDelay;
 
-      beforeEach(function() {
+      beforeEach(function () {
         retryDelay = 5000;
         options = {
           retryDelay: retryDelay
@@ -432,31 +444,31 @@ describe('fetch-retry', function() {
           .then(thenCallback);
       });
 
-      describe('when first call is unsuccessful', function() {
+      describe('when first call is unsuccessful', function () {
 
-        beforeEach(function() {
+        beforeEach(function () {
           deferred1.reject();
         });
 
-        describe('after specified time', function() {
+        describe('after specified time', function () {
 
-          beforeEach(function() {
+          beforeEach(function () {
             clock.tick(retryDelay);
           });
 
-          it('invokes fetch again', function() {
+          it('invokes fetch again', function () {
             expect(fetch.callCount).toBe(2);
           });
 
         });
 
-        describe('after less than specified time', function() {
+        describe('after less than specified time', function () {
 
-          beforeEach(function() {
+          beforeEach(function () {
             clock.tick(1000);
           });
 
-          it('does not invoke fetch again', function() {
+          it('does not invoke fetch again', function () {
             expect(fetch.callCount).toBe(1);
           });
 
@@ -466,12 +478,12 @@ describe('fetch-retry', function() {
 
     });
 
-    describe('when #options.retryDelay is 0', function() {
+    describe('when #options.retryDelay is 0', function () {
 
       var options;
       var retryDelay;
 
-      beforeEach(function() {
+      beforeEach(function () {
         retryDelay = 0;
         options = {
           retryDelay: retryDelay
@@ -483,19 +495,19 @@ describe('fetch-retry', function() {
           .then(thenCallback);
       });
 
-      describe('when first call is unsuccessful', function() {
+      describe('when first call is unsuccessful', function () {
 
-        beforeEach(function() {
+        beforeEach(function () {
           deferred1.reject();
         });
 
-        describe('after one event loop tick', function() {
+        describe('after one event loop tick', function () {
 
-          beforeEach(function() {
+          beforeEach(function () {
             clock.tick(0);
           });
 
-          it('invokes fetch again', function() {
+          it('invokes fetch again', function () {
             expect(fetch.callCount).toBe(2);
           });
 
@@ -523,12 +535,12 @@ describe('fetch-retry', function() {
 
     });
 
-    describe('when #options.retryDelay is a function', function() {
+    describe('when #options.retryDelay is a function', function () {
 
       var options;
       var retryDelay;
 
-      beforeEach(function() {
+      beforeEach(function () {
         retryDelay = sinon.stub().returns(5000);
         options = {
           retryDelay: retryDelay
@@ -540,20 +552,20 @@ describe('fetch-retry', function() {
           .then(thenCallback);
       });
 
-      describe('when first call is unsuccessful', function() {
+      describe('when first call is unsuccessful', function () {
 
-        beforeEach(function() {
+        beforeEach(function () {
           deferred1.reject(new Error('first error'));
         });
 
-        describe('when the second call is a success', function() {
+        describe('when the second call is a success', function () {
 
-          beforeEach(function() {
+          beforeEach(function () {
             deferred2.resolve({ status: 200 });
             clock.tick(5000);
           });
 
-          it('invokes the retryDelay function', function() {
+          it('invokes the retryDelay function', function () {
             expect(retryDelay.called).toBe(true);
             expect(retryDelay.lastCall.args[0]).toEqual(0);
             expect(retryDelay.lastCall.args[1].message).toEqual('first error');
@@ -562,21 +574,21 @@ describe('fetch-retry', function() {
 
         });
 
-        describe('when second call is a failure', function() {
+        describe('when second call is a failure', function () {
 
-          beforeEach(function() {
+          beforeEach(function () {
             deferred2.reject(new Error('second error'));
             clock.tick(5000);
           });
 
-          describe('when the third call is a success', function() {
+          describe('when the third call is a success', function () {
 
-            beforeEach(function() {
+            beforeEach(function () {
               deferred3.resolve({ status: 200 });
               clock.tick(5000);
             });
 
-            it('invokes the retryDelay function again', function() {
+            it('invokes the retryDelay function again', function () {
               expect(retryDelay.callCount).toBe(2);
               expect(retryDelay.lastCall.args[0]).toEqual(1);
               expect(retryDelay.lastCall.args[1].message).toEqual('second error');
@@ -599,7 +611,7 @@ describe('fetch-retry', function() {
       var options;
       var retryOn;
 
-      beforeEach(function() {
+      beforeEach(function () {
         retryOn = [503, 404];
         options = {
           retryOn: retryOn
@@ -616,7 +628,7 @@ describe('fetch-retry', function() {
       describe('when first fetch is resolved with status code specified in retryOn array', () => {
 
         beforeEach(() => {
-          deferred1.resolve({status: 503});
+          deferred1.resolve({ status: 503 });
         });
 
         describe('after specified delay', () => {
@@ -632,16 +644,16 @@ describe('fetch-retry', function() {
           describe('when second fetch resolves with a different status code', () => {
 
             beforeEach(() => {
-              deferred2.resolve({status: 200});
+              deferred2.resolve({ status: 200 });
             });
 
             describe('when resolved', () => {
 
-              it('invokes the then callback', function() {
+              it('invokes the then callback', function () {
                 expect(thenCallback.called).toBe(true);
               });
 
-              it('has called fetch twice', function() {
+              it('has called fetch twice', function () {
                 expect(fetch.callCount).toBe(2);
               });
 
@@ -655,12 +667,12 @@ describe('fetch-retry', function() {
 
     });
 
-    describe('when #options.retryOn is a function', function() {
+    describe('when #options.retryOn is a function', function () {
 
       var options;
       var retryOn;
 
-      beforeEach(function() {
+      beforeEach(function () {
         retryOn = sinon.stub();
         options = {
           retryOn: retryOn
@@ -674,18 +686,18 @@ describe('fetch-retry', function() {
           .catch((catchCallback));
       });
 
-      describe('when first attempt is rejected due to network error', function() {
+      describe('when first attempt is rejected due to network error', function () {
 
         describe('when #retryOn() returns true', () => {
 
-          beforeEach(function() {
+          beforeEach(function () {
             retryOn.returns(true);
             deferred1.reject(new Error('first error'));
           });
 
-          describe('when rejected', function() {
+          describe('when rejected', function () {
 
-            it('invokes #retryOn function with an error', function() {
+            it('invokes #retryOn function with an error', function () {
               expect(retryOn.called).toBe(true);
               expect(retryOn.lastCall.args.length).toBe(3);
               expect(retryOn.lastCall.args[0]).toBe(0);
@@ -693,26 +705,26 @@ describe('fetch-retry', function() {
               expect(retryOn.lastCall.args[2]).toBe(null);
             });
 
-            describe('after specified time', function() {
+            describe('after specified time', function () {
 
-              beforeEach(function() {
+              beforeEach(function () {
                 clock.tick(delay);
               });
 
-              it('invokes fetch again', function() {
+              it('invokes fetch again', function () {
                 expect(fetch.callCount).toBe(2);
               });
 
-              describe('when the second call is unsuccessful', function() {
+              describe('when the second call is unsuccessful', function () {
 
-                beforeEach(function() {
+                beforeEach(function () {
                   deferred2.reject(new Error('second error'));
                   clock.tick(delay);
                 });
 
-                describe('when rejected', function() {
+                describe('when rejected', function () {
 
-                  it('invokes the #retryOn function twice', function() {
+                  it('invokes the #retryOn function twice', function () {
                     expect(retryOn.callCount).toBe(2);
                     expect(retryOn.lastCall.args[0]).toBe(1);
                   });
@@ -729,14 +741,14 @@ describe('fetch-retry', function() {
 
         describe('when #retryOn() returns false', () => {
 
-          beforeEach(function() {
+          beforeEach(function () {
             retryOn.returns(false);
             deferred1.reject(new Error('first error'));
           });
 
-          describe('when rejected', function() {
+          describe('when rejected', function () {
 
-            it('invokes #retryOn function with an error', function() {
+            it('invokes #retryOn function with an error', function () {
               expect(retryOn.called).toBe(true);
               expect(retryOn.lastCall.args.length).toBe(3);
               expect(retryOn.lastCall.args[0]).toBe(0);
@@ -744,17 +756,17 @@ describe('fetch-retry', function() {
               expect(retryOn.lastCall.args[2]).toBe(null);
             });
 
-            describe('after specified time', function() {
+            describe('after specified time', function () {
 
-              beforeEach(function() {
+              beforeEach(function () {
                 clock.tick(delay);
               });
 
-              it('invokes the catch callback', function() {
+              it('invokes the catch callback', function () {
                 expect(catchCallback.called).toBe(true);
               });
 
-              it('does not call fetch again', function() {
+              it('does not call fetch again', function () {
                 expect(fetch.callCount).toBe(1);
               });
 
@@ -766,33 +778,33 @@ describe('fetch-retry', function() {
 
       });
 
-      describe('when first attempt is resolved', function() {
+      describe('when first attempt is resolved', function () {
 
         describe('when #retryOn() returns true', () => {
 
-          beforeEach(function() {
+          beforeEach(function () {
             retryOn.returns(true);
             deferred1.resolve({ status: 200 });
           });
 
           describe('after specified delay', () => {
 
-            beforeEach(function() {
+            beforeEach(function () {
               clock.tick(delay);
             });
 
-            it('calls fetch again', function() {
+            it('calls fetch again', function () {
               expect(fetch.callCount).toBe(2);
             });
 
             describe('when second call is resolved', () => {
 
-              beforeEach(function() {
+              beforeEach(function () {
                 deferred2.resolve({ status: 200 });
                 clock.tick(delay);
               });
 
-              it('invokes the #retryOn function with the response', function() {
+              it('invokes the #retryOn function with the response', function () {
                 expect(retryOn.called).toBe(true);
                 expect(retryOn.lastCall.args.length).toBe(3);
                 expect(retryOn.lastCall.args[0]).toBe(0);
@@ -808,18 +820,18 @@ describe('fetch-retry', function() {
 
         describe('when #retryOn() returns false', () => {
 
-          beforeEach(function() {
+          beforeEach(function () {
             retryOn.returns(false);
             deferred1.resolve({ status: 502 });
           });
 
           describe('when resolved', () => {
 
-            it('invokes the then callback', function() {
+            it('invokes the then callback', function () {
               expect(thenCallback.called).toBe(true);
             });
 
-            it('calls fetch 1 time only', function() {
+            it('calls fetch 1 time only', function () {
               expect(fetch.callCount).toBe(1);
             });
 
@@ -831,14 +843,14 @@ describe('fetch-retry', function() {
 
     });
 
-    describe('when #options.retryOn is not an array or function', function() {
+    describe('when #options.retryOn is not an array or function', function () {
 
       var options;
 
       describe('when #options.retryOn is not an array or function', () => {
 
         it('throws exception', () => {
-          expect(function() {
+          expect(function () {
             options.retryOn = 503;
             fetchRetry('http://someUrl', options);
           }).toThrow({
@@ -857,7 +869,7 @@ describe('fetch-retry', function() {
 
 function defer() {
   var resolve, reject;
-  var promise = new Promise(function() {
+  var promise = new Promise(function () {
     resolve = arguments[0];
     reject = arguments[1];
   });