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=68eb2671&is=68e9d4f1&hm=6f8b46292fdcd2e96fc526169b25148cf3ad890b49db0340c2d326c459aaf118& https://cdn.discordapp.com/attachments/882985025803530332/1426236441737822318/image.png?ex=68eb2671&is=68e9d4f1&hm=6901a35e6a8137002c8985cecba35b232becc405d93c0fe5c871d5c9df39f3d3&

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 🤔