Add a test for running ghc in a nix-shell

Author: rvl

test/tests.sh

@@ -24,5 +24,12 @@ printf "*** Checking that a nix-shell works for cabal...\n" >& 2
 nix-shell --pure ./default.nix \
     -A with-packages.test-shell \
     --run 'echo CABAL_CONFIG=$CABAL_CONFIG && cd with-packages && cabal new-build'
+echo >& 2
+
+printf "*** Checking that a nix-shell works for runghc...\n" >& 2
+nix-shell --pure ./default.nix \
+    -A with-packages.test-shell \
+    --run 'runghc with-packages/Point.hs'
+echo >& 2
 
 printf "\n*** Finished successfully\n" >& 2