I managed to get what I set out to achieve today working in the most crude manner. I can now inherit UmbracoIntegrationTest in a "setup fixture" and use the Umbraco instance and services in all test fixtures under the same namespace. Wrote up a discussion post here: https://github.com/umbraco/Umbraco-CMS/discussions/20465 And the repo can be admired here: https://github.com/lars-erik/NUnitCompositionWithUmbraco Cheers for a lovely hangout to everyone on zoom. Attached are a couple of screenshots showing the "gist of it". 🥳 https://cdn.discordapp.com/attachments/882985025803530332/1426236440966201486/image.png?ex=6978dfb1&is=69778e31&hm=10ebfd132d8ae880bc87a46b73be22e165fa043dba6913034b236cd415762f48& https://cdn.discordapp.com/attachments/882985025803530332/1426236441737822318/image.png?ex=6978dfb1&is=69778e31&hm=2d594bd266bbacfafd1f42532846b64cf06632c9a35c419e0030cec2c0f3f40c&

Is there any reason why you choosed nunit? Personally i go after xunit, because it is faster and works better with parallel tests. Also resource usage is lower, which means it cost less to run tests 🤔