When enabling activesupport/minitest's random test ordering on Rails 4.2, some failures are seen:

Some when executing Api::V2 OS controller tests in this order:

10:10:13 Api::V2::OperatingsystemsControllerTest#test_0005_should not create os without version = 0.11 s = .
10:10:13 Api::V2::OperatingsystemsControllerTest#test_0014_should show os if id is description = 0.14 s = .
10:10:13 Api::V2::OperatingsystemsControllerTest#test_0013_should show os if id is fullname = 0.10 s = .
10:10:13 Api::V2::OperatingsystemsControllerTest#test_0009_should update associated architectures by name with UNWRAPPED node = 0.16 s = .
10:10:13 Api::V2::OperatingsystemsControllerTest#test_0004_should create os with os parameters = 0.01 s = E
10:10:13 Api::V2::OperatingsystemsControllerTest#test_0011_should add association of architectures by name with WRAPPED node = 0.17 s = .
10:10:13 Api::V2::OperatingsystemsControllerTest#test_0006_should update os = 0.14 s = .
10:10:13 Api::V2::OperatingsystemsControllerTest#test_0001_should get index = 0.06 s = .
10:10:14 Api::V2::OperatingsystemsControllerTest#test_0010_should add association of architectures by ids with WRAPPED node = 0.51 s = .
10:10:14 Api::V2::OperatingsystemsControllerTest#test_0003_should create os = 0.06 s = F
10:10:14 Api::V2::OperatingsystemsControllerTest#test_0008_should update associated architectures by ids with UNWRAPPED node = 0.16 s = .
10:10:14 Api::V2::OperatingsystemsControllerTest#test_0002_should show os = 0.13 s = .
10:10:14 Api::V2::OperatingsystemsControllerTest#test_0007_should destroy os = 0.08 s = .
10:10:15 Api::V2::OperatingsystemsControllerTest#test_0012_should remove association of architectures with WRAPPED node = 0.16 s = .

This functional test has a class-level os variable which is being reassigned with OS resources.

And also seed tests in this order:

SeedsTest::populating an initial admin user#test_0002_with environment overrides = 6.05 s = .
SeedsTest::populating an initial admin user#test_0001_with defaults = 5.61 s = F

This unit test uses the with_env helper, which doesn't unset previously unassigned environment variables on completion.