Fixes for test failures caused by undefined window.matchMedia

src/js/__tests__/addFile.test.js

@@ -1,3 +1,4 @@
+import "./windowMatchMedia.mock";
 import { create } from '../index.js';
 
 describe('adding files', () => {

src/js/__tests__/callbacks.test.js

@@ -1,3 +1,4 @@
+import "./windowMatchMedia.mock";
 import { create, OptionTypes, FileStatus } from '../index.js';
 
 describe('adding files', () => {

src/js/__tests__/createInstance.test.js

@@ -1,3 +1,4 @@
+import "./windowMatchMedia.mock";
 import { create } from '../index.js';
 
 describe('create instance', () => {

src/js/__tests__/removeFile.test.js

@@ -1,3 +1,4 @@
+import "./windowMatchMedia.mock";
 import { create } from '../index.js';
 
 const server = {

src/js/__tests__/server.test.js

@@ -1,3 +1,4 @@
+import "./windowMatchMedia.mock";
 import { create } from '../index.js';
 
 describe('setting server property', () => {

src/js/__tests__/setFiles.test.js

@@ -1,3 +1,4 @@
+import "./windowMatchMedia.mock";
 import { create } from '../index.js';
 
 const next = (cb) => {

src/js/__tests__/windowMatchMedia.mock

@@ -0,0 +1,17 @@
+// Mocking window.matchMedia as described in the jest docks
+// since this is not defined in JSDOM and causes the tests
+// to fail. See: "https://jestjs.io/docs/en/manual-
+// mocks#mocking-methods-which-are-not-implemented-in-jsdom"
+Object.defineProperty(window, 'matchMedia', {
+    writable: true,
+    value: jest.fn().mockImplementation(query => ({
+        matches: false,
+        media: query,
+        onchange: null,
+        addListener: jest.fn(), // deprecated
+        removeListener: jest.fn(), // deprecated
+        addEventListener: jest.fn(),
+        removeEventListener: jest.fn(),
+        dispatchEvent: jest.fn(),
+    })),
+});