After upgrading to NUnit 3.0, which became recently available, some of my tests started to fail. When I look at the test results, they all failed with the following error message: SetUpAttribute attribute not allowed in a SetUpFixture In NUnit 3.0, there are some breaking changes regarding the usage of the SetUpAttribute and the SetUpFixture. You can no longer use the SetUpAttribute and TearDownAttribute inside a SetUpFixture. Instead you have to use the OneTimeSetUpAttribute and OneTimeTearDownAttribute. In NUnit 2.0, I had the following code: In NUnit 3.0, this has to change to: More information can be found here: https://github.com/nunit/nunit/wiki/SetUp-and-TearDown-Changes https://github.com/nunit/nunit/wiki/Breaking-Changes