diff --git a/.eslintignore.errorfiles b/.eslintignore.errorfiles
index 4584d7ed65..ffd492d491 100644
--- a/.eslintignore.errorfiles
+++ b/.eslintignore.errorfiles
@@ -146,7 +146,6 @@ src/Roles.js
 src/RoomListSorter.js
 src/RoomNotifs.js
 src/Rooms.js
-src/RtsClient.js
 src/ScalarAuthClient.js
 src/ScalarMessaging.js
 src/SdkConfig.js
diff --git a/src/RtsClient.js b/src/RtsClient.js
index 8c3ce54b37..493b19599c 100644
--- a/src/RtsClient.js
+++ b/src/RtsClient.js
@@ -1,5 +1,7 @@
 import 'whatwg-fetch';
 
+let fetchFunction = fetch;
+
 function checkStatus(response) {
     if (!response.ok) {
         return response.text().then((text) => {
@@ -31,7 +33,7 @@ const request = (url, opts) => {
         opts.body = JSON.stringify(opts.body);
         opts.headers['Content-Type'] = 'application/json';
     }
-    return fetch(url, opts)
+    return fetchFunction(url, opts)
         .then(checkStatus)
         .then(parseJson);
 };
@@ -64,7 +66,7 @@ export default class RtsClient {
                     client_secret: clientSecret,
                 },
                 method: 'POST',
-            }
+            },
         );
     }
 
@@ -74,7 +76,7 @@ export default class RtsClient {
                 qs: {
                     team_token: teamToken,
                 },
-            }
+            },
         );
     }
 
@@ -91,7 +93,12 @@ export default class RtsClient {
                 qs: {
                     user_id: userId,
                 },
-            }
+            },
         );
     }
+
+    // allow fetch to be replaced, for testing.
+    static setFetch(fn) {
+        fetchFunction = fn;
+    }
 }
diff --git a/src/index.js b/src/index.js
index 7d0547d9c9..8c290fcb64 100644
--- a/src/index.js
+++ b/src/index.js
@@ -15,6 +15,7 @@ limitations under the License.
 */
 
 import Skinner from './Skinner';
+import RtsClient from './RtsClient';
 
 module.exports.loadSkin = function(skinObject) {
     Skinner.load(skinObject);
@@ -27,3 +28,7 @@ module.exports.resetSkin = function() {
 module.exports.getComponent = function(componentName) {
     return Skinner.getComponent(componentName);
 };
+
+module.exports.setFetch = function(fetchFunction) {
+    RtsClient.setFetch(fetchFunction);
+};