I use a 'T' prefix for test namespaces, classes and methods.
I try to be neat and create folders that replicate the namespaces, then create a tests folder or separate project for the tests and replicate the production structure for the basic tests:
AProj
Objects
AnObj
AProp
Misc
Functions
AFunc
Tests
TObjects
TAnObj
TAnObjsAreEqualUnderCondition
TMisc
TFunctions
TFuncBehavesUnderCondition
I can easily see that something is a test, I know exactly what original code it pertains to, (if you can't work that out, then the test is too convoluted anyway).
It looks just like the interfaces naming convention, (I mean, you don't get confused with things starting with 'I', nor will you with 'T').
It's easy to just compile with or without the tests.
It's good in theory anyway, and works pretty well for small projects.
