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diff --git a/javascript/videojs/test/unit/mixins/stateful.test.js b/javascript/videojs/test/unit/mixins/stateful.test.js
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+++ b/javascript/videojs/test/unit/mixins/stateful.test.js
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+/* eslint-env qunit */
+import sinon from 'sinon';
+import evented from '../../../src/js/mixins/evented';
+import stateful from '../../../src/js/mixins/stateful';
+import * as Obj from '../../../src/js/utils/obj';
+
+QUnit.module('mixins: stateful');
+
+QUnit.test('stateful() mutates an object as expected', function(assert) {
+  const target = {};
+
+  assert.strictEqual(Object.prototype.toString.call(stateful), '[object Function]', 'the mixin is a function');
+  assert.strictEqual(stateful(target), target, 'returns the target object');
+
+  assert.ok(Obj.isObject(target), 'the target is still an object');
+  assert.ok(Obj.isPlain(target.state), 'the target has a state');
+  assert.strictEqual(Object.keys(target.state).length, 0, 'the target state is empty by default');
+  assert.strictEqual(Object.prototype.toString.call(target.setState), '[object Function]', 'the target has a setState method');
+});
+
+QUnit.test('stateful() with default state passed in', function(assert) {
+  const target = stateful({}, {foo: 'bar'});
+
+  assert.strictEqual(target.state.foo, 'bar', 'the default properties are added to the state');
+});
+
+QUnit.test('stateful() without default state passed in', function(assert) {
+  const target = stateful({});
+
+  assert.strictEqual(Object.keys(target.state).length, 0, 'no default properties are added to the state');
+});
+
+QUnit.test('setState() works as expected', function(assert) {
+  const target = stateful(evented({}), {foo: 'bar', abc: 'xyz'});
+  const spy = sinon.spy();
+
+  target.on('statechanged', spy);
+
+  const next = {foo: null, boo: 123};
+  const changes = target.setState(next);
+
+  assert.deepEqual(changes, {
+    foo: {from: 'bar', to: null},
+    boo: {from: undefined, to: 123}
+  }, 'setState returns changes, a plain object');
+
+  assert.deepEqual(target.state, {
+    abc: 'xyz',
+    foo: null,
+    boo: 123
+  }, 'the state was updated as expected');
+
+  assert.ok(spy.called, 'the "statechanged" event occurred');
+
+  const event = spy.firstCall.args[0];
+
+  assert.strictEqual(event.type, 'statechanged', 'the event had the expected type');
+  assert.strictEqual(event.changes, changes, 'the changes object is sent along with the event');
+
+  target.trigger('dispose');
+});
+
+QUnit.test('setState() without changes does not trigger the "statechanged" event', function(assert) {
+  const target = stateful(evented({}), {foo: 'bar'});
+  const spy = sinon.spy();
+
+  target.on('statechanged', spy);
+
+  const changes = target.setState({foo: 'bar'});
+
+  assert.strictEqual(changes, undefined, 'no changes were returned');
+  assert.strictEqual(spy.callCount, 0, 'no event was triggered');
+  target.trigger('dispose');
+});
+
+QUnit.test('handleStateChanged() is automatically bound to "statechanged" event', function(assert) {
+  const target = evented({});
+
+  target.handleStateChanged = sinon.spy();
+  stateful(target, {foo: 'bar'});
+
+  const changes = target.setState({foo: true});
+
+  assert.ok(target.handleStateChanged.called, 'the "statechanged" event occurred');
+
+  const event = target.handleStateChanged.firstCall.args[0];
+
+  assert.strictEqual(event.type, 'statechanged', 'the event had the expected type');
+  assert.strictEqual(event.changes, changes, 'the handleStateChanged() method was called');
+  target.trigger('dispose');
+});