Tests should work now.

default.nix

@@ -6,6 +6,8 @@
 }:
 let
   masterPkgs = import sources.nixpkgs { inherit system; };
+  yq = import ./nix/yq.nix { pkgs = masterPkgs; };
+  diffYaml = import ./nix/diff-yaml.nix { pkgs = masterPkgs; };
 
   hsPkgs = pkgs.haskell-nix.stackProject {
     src = nix-filter {
@@ -97,6 +99,18 @@ let
     };
 
   WindowsCompaRESTBin = hsPkgs.projectCross.mingwW64.hsPkgs.compaREST.components.exes.compaREST;
+
+  # We use the static version so that we don't have to rebuild everything on CI.
+  # The only binaries build on CI are static.
+  test = hsPkgs.projectCross.musl64.hsPkgs.compaREST.components.tests.compaREST-tests.overrideAttrs (final: old: {
+    buildInputs = old.buildInputs ++ [ diffYaml yq ];
+    nativeBuildInputs = old.nativeBuildInputs ++ (with masterPkgs; [ makeWrapper ]);
+
+    postInstall = ''
+      wrapProgram $out/bin/compaREST-tests \
+        --prefix PATH : ${masterPkgs.lib.makeBinPath [ diffYaml yq ]}
+    '';
+  });
 in
 {
   inherit
@@ -106,9 +120,6 @@ in
     compaRESTBin
     hsPkgs
     macOSCompaRESTBundle
-    WindowsCompaRESTBin;
-
-  # We use the static version so that we don't have to rebuild everything on CI.
-  # The only binaries build on CI are static.
-  test = hsPkgs.projectCross.musl64.hsPkgs.compaREST.components.tests.compaREST-tests;
+    WindowsCompaRESTBin
+    test;
 }

nix/ci.nix

@@ -1,6 +1,11 @@
 { sources ? import ./sources.nix
 , pkgs ? import sources.nixpkgs { }
 }:
+
+let
+  yq = import ./yq.nix { inherit pkgs; };
+  diff-yaml = import ./diff-yaml.nix { inherit pkgs; };
+in
 pkgs.mkShell {
-  packages = [ pkgs.haskellPackages.fourmolu ];
+  packages = [ pkgs.haskellPackages.fourmolu diff-yaml yq ];
 }

nix/diff-yaml.nix

@@ -0,0 +1,20 @@
+{ pkgs ? import <nixpkgs> {} }:
+
+let
+  inherit (pkgs) stdenv;
+  yq = import ./yq.nix { inherit pkgs; };
+in
+stdenv.mkDerivation {
+  name = "diff-yaml";
+
+  src = ../scripts/diff-yaml;
+
+  buildInputs = [ pkgs.bash yq ];
+
+  phases = [ "installPhase" ];
+
+  installPhase = ''
+    mkdir -p $out/bin
+    cp $src $out/bin/diff-yaml
+  '';
+}

nix/sources.json

@@ -5,10 +5,10 @@
         "homepage": "https://input-output-hk.github.io/haskell.nix",
         "owner": "input-output-hk",
         "repo": "haskell.nix",
-        "rev": "c1382b31f1ba8440acf409babf78f3139f415318",
-        "sha256": "1bf2d0wq7l1v2gbds4is9diqm9821dgc9pgqs9vnx8d1zw4mq10f",
+        "rev": "4413d8325d6359a6be774ef07d9a310ab96c4d25",
+        "sha256": "0il11752dv2pn47i3kynjfgikfwn2rm4naray89xm8dlgafk90mj",
         "type": "tarball",
-        "url": "https://github.com/input-output-hk/haskell.nix/archive/c1382b31f1ba8440acf409babf78f3139f415318.tar.gz",
+        "url": "https://github.com/input-output-hk/haskell.nix/archive/4413d8325d6359a6be774ef07d9a310ab96c4d25.tar.gz",
         "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
     },
     "niv": {
@@ -41,10 +41,10 @@
         "homepage": "",
         "owner": "NixOS",
         "repo": "nixpkgs",
-        "rev": "619de33c2d7bdcf6f03fc1f5d4d9d33df3ae7261",
-        "sha256": "1pybxai356n7phqn85iicydl67x5qqbb7ssncddlxcpy1qbxih06",
+        "rev": "3c89ee1b7bc3121a8f7d2303163e45320bb75eba",
+        "sha256": "1jx033mxi3pcz0whplzni2d7dra95r3pn3vgdrjlrbj26x19j49z",
         "type": "tarball",
-        "url": "https://github.com/NixOS/nixpkgs/archive/619de33c2d7bdcf6f03fc1f5d4d9d33df3ae7261.tar.gz",
+        "url": "https://github.com/NixOS/nixpkgs/archive/3c89ee1b7bc3121a8f7d2303163e45320bb75eba.tar.gz",
         "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
     }
 }

nix/yq.nix

@@ -1,6 +1,8 @@
 { pkgs ? import <nixpkgs> {} }:
 
 # Make yq work inside whatever `stack test` launches.
+# Nuke this when https://github.com/kislyuk/yq/pull/193 is merged
+# and nixpkgs includes that fix.
 
 let
   yq-patch = pkgs.writeText "yq-tty-fix.patch" ''

scripts/diff-yaml

@@ -0,0 +1,35 @@
+#!/usr/bin/env bash
+set -e
+
+# Normalise YAML files passed as inputs, then run diff on them.
+
+check_util() {
+  local util=$1
+
+  if [ -z $util ]; then
+     echo "Error: $util not found in PATH"
+     exit 1
+  fi
+}
+
+DIFF=`which diff`
+check_util $DIFF
+
+YQ=`which yq`
+check_util $YQ
+
+# Only normalise YAML files.
+# Print anything else as is.
+normalise() {
+  local file=$1
+  local contents=($YQ -y -S '.' $file)
+
+  # if $contents contains actual YAML data, print it
+  if [[ $? == 0 ]]; then
+     echo $contents
+  else
+      cat $file
+  fi
+}
+
+$DIFF -u <(normalise $1) <(normalise $2)

stack.yaml

@@ -16,4 +16,6 @@ extra-deps:
 allow-newer: true
 
 nix:
-  packages: [pkg-config zlib]
+#  packages: [pkg-config yq zlib]
+  shell-file: ./nix/shell.nix
+  pure: false

test/Spec/Golden/Extra.hs

@@ -59,7 +59,7 @@ goldenInputsTree ::
   s ->
   (t -> IO BSL.ByteString) ->
   IO TestTree
-goldenInputsTree name filepath golden inp f = do
+goldenInputsTree name filepath golden inp f =
   runTestInputTree golden f <$> getGoldenInputs name filepath inp
 
 runTestInputTree ::