haskellPackages.persistent-postgresql: Enable tests

pkgs/development/haskell-modules/configuration-common.nix

@@ -1331,7 +1331,25 @@ self: super: {
 
   # Test suite requires database
   persistent-mysql = dontCheck super.persistent-mysql;
-  persistent-postgresql = dontCheck super.persistent-postgresql;
+  persistent-postgresql =
+    overrideCabal
+      (drv: {
+        postPatch = drv.postPath or "" + ''
+          # patch out TCP usage: https://nixos.org/manual/nixpkgs/stable/#sec-postgresqlTestHook-tcp
+          # NOTE: upstream host variable takes only two values...
+          sed -i test/PgInit.hs \
+            -e s^'host=" <> host <> "'^^
+        '';
+        preCheck = drv.preCheck or "" + ''
+          PGDATABASE=test
+          PGUSER=test
+        '';
+        testToolDepends = drv.testToolDepends or [] ++ [
+          pkgs.postgresql
+          pkgs.postgresqlTestHook
+        ];
+      })
+      super.persistent-postgresql;
 
   # Fix EdisonAPI and EdisonCore for GHC 8.8:
   # https://github.com/robdockins/edison/pull/16