Added custom app for testing. Added tests framework and runner.

.gitignore

 *.pyc
 *.egg-info
 dist/
+./settings.py
+venv/

runtests.py

+#!/usr/bin/env python3
+
+import os
+import shutil
+import sys
+
+
+def run():
+    from django.core.management import execute_from_command_line
+    os.environ['DJANGO_SETTINGS_MODULE'] = 'tests.app.settings'
+    try:
+        execute_from_command_line([sys.argv[0], 'test'] + sys.argv[1:])
+    finally:
+        from tests.app.settings import STATIC_ROOT, MEDIA_ROOT
+        shutil.rmtree(STATIC_ROOT, ignore_errors=True)
+        shutil.rmtree(MEDIA_ROOT, ignore_errors=True)
+
+if __name__ == '__main__':
+    run()

settings.py

+from tests.app.settings import *
+
+DATABASES = {
+    'default': {
+        'ENGINE': 'django.db.backends.sqlite3',
+        'NAME': 'tests.sqlite3',
+    },
+}

tests/app/migrations/0001_initial.py

+# -*- coding: utf-8 -*-
+# Generated by Django 1.9.7 on 2016-07-11 02:19
+from __future__ import unicode_literals
+
+from django.db import migrations, models
+import django.db.models.deletion
+
+
+class Migration(migrations.Migration):
+
+    initial = True
+
+    dependencies = [
+        ('wagtailcore', '0028_merge'),
+        ('wagtailvideos', '0007_video_duration'),
+    ]
+
+    operations = [
+        migrations.CreateModel(
+            name='TestPage',
+            fields=[
+                ('page_ptr', models.OneToOneField(auto_created=True, on_delete=django.db.models.deletion.CASCADE, parent_link=True, primary_key=True, serialize=False, to='wagtailcore.Page')),
+                ('video_field', models.ForeignKey(blank=True, null=True, on_delete=django.db.models.deletion.SET_NULL, related_name='+', to='wagtailvideos.Video')),
+            ],
+            options={
+                'abstract': False,
+            },
+            bases=('wagtailcore.page',),
+        ),
+    ]

tests/app/models.py

+from django.db import models
+from wagtail.wagtailcore.models import Page
+
+from wagtailvideos.edit_handlers import VideoChooserPanel
+
+
+class TestPage(Page):
+    video_field = models.ForeignKey('wagtailvideos.Video', related_name='+', null=True, blank=True, on_delete=models.SET_NULL)
+
+    content_panels = Page.content_panels + [
+        VideoChooserPanel('video_field')
+    ]

tests/app/settings.py

+import os
+import sys
+
+INSTALLED_APPS = [
+    'wagtailvideos',
+    'tests.app',
+
+    'taggit',
+    'modelcluster',
+
+    'wagtail.wagtailcore',
+    'wagtail.wagtailadmin',
+    'wagtail.wagtailusers',
+    'wagtail.wagtailsites',
+    'wagtail.wagtailsnippets',
+
+    'django.contrib.admin',
+    'django.contrib.auth',
+    'django.contrib.contenttypes',
+    'django.contrib.sessions',
+    'django.contrib.staticfiles',
+]
+
+SECRET_KEY = 'not a secret'
+
+ROOT_URLCONF = 'tests.app.urls'
+
+DATABASES = {
+    'default': {
+        'ENGINE': 'django.db.backends.sqlite3',
+        'NAME': ':memory:',
+    },
+}
+
+WAGTAIL_SITE_NAME = 'Wagtail Videos'
+
+DEBUG = True
+
+USE_TZ = True
+TIME_ZONE = 'Australia/Hobart'
+
+MIDDLEWARE_CLASSES = [
+    'django.contrib.sessions.middleware.SessionMiddleware',
+    'django.middleware.common.CommonMiddleware',
+    'django.middleware.csrf.CsrfViewMiddleware',
+    'django.contrib.auth.middleware.AuthenticationMiddleware',
+    'django.contrib.messages.middleware.MessageMiddleware',
+    'django.middleware.clickjacking.XFrameOptionsMiddleware',
+
+    'wagtail.wagtailcore.middleware.SiteMiddleware',
+]
+
+TEMPLATES = [
+    {
+        'BACKEND': 'django.template.backends.django.DjangoTemplates',
+        'APP_DIRS': True,
+        'OPTIONS': {
+            'context_processors': [
+                'django.contrib.auth.context_processors.auth',
+                'django.template.context_processors.debug',
+                'django.template.context_processors.i18n',
+                'django.template.context_processors.media',
+                'django.template.context_processors.static',
+                'django.template.context_processors.tz',
+                'django.template.context_processors.request',
+                'django.contrib.messages.context_processors.messages'
+            ],
+        },
+    },
+]
+
+STATIC_ROOT = os.path.join(os.path.dirname(__file__), 'static')
+STATIC_URL = '/static/'
+
+MEDIA_ROOT = os.path.join(os.path.dirname(__file__), 'media')

tests/app/urls.py

+from django.conf.urls import include, url
+from wagtail.wagtailadmin import urls as wagtailadmin_urls
+from wagtail.wagtailcore import urls as wagtail_urls
+
+urlpatterns = [
+    url(r'^admin/', include(wagtailadmin_urls)),
+    url(r'', include(wagtail_urls)),
+]

tests/test_template_tag.py

+import unittest
+
+from django.test import TestCase
+
+from tests.utils import create_test_video
+from wagtailvideos.models import Video
+
+
+class TestVideoTag(TestCase):
+    def setUp(self):
+        self.video = Video.objects.create(
+            title="Test Video",
+            file=create_test_video()
+        )
+
+    def test_whatever(self):
+        print(self.video.file.path)
+        pass

tests/utils.py

+import os
+
+from django.core.files import File
+
+import tests
+
+
+def create_test_video():
+    video_file = open(os.path.join(tests.__path__[0], 'small.mp4'), 'rb')
+    return File(video_file, name='small.mp4')