Haskell module imports itself

Question

I have src/Main.hs define the Main module and tests/Tests.hs import the Main module. Why does cabal build tell me module 'Main' (tests/Tests.hs) imports itself?

Answer 1

Did you give Tests a module header?

module Tests where

import Main

-- ...

Also, depending on the testing framework, test suites are usually run as a standalone executable with their own main, importing common modules that Main also uses.