When building this nix expression I get the following failure:

$ nix-build
...
running tests
Running 1 test suites...
Test suite test-myLib: RUNNING...
test-myLib: /tmp/nix-build-myLib-0.0.0.drv-0/hs-test-failure-nix/Lenna.png doesn't exist!

The reason is that the test suite can't find the data file Lenna.png because the Paths_myLib module specifies the wrong paths. Running the test-suite manually works if I set the environment variable myLib_datadir=data:

$ nix-shell --command 'cabal configure --enable-tests; cabal build; myLib_datadir=data dist/build/test-myLib/test-myLib'

Also interesting is that it also fails if I use cabal test instead of running the test executable manually:

$ nix-shell --command 'cabal configure --enable-tests; cabal build; myLib_datadir=data cabal test'
...
Running 1 test suites...
Test suite test-myLib: RUNNING...
test-myLib: /home/bas.van.dijk/development/hs-test-failure-nix/Lenna.png doesn't exist!

Any idea how to get the test suite to run when building with nix-build?