tests: add small testcase for output cycle detection

Change-Id: I186937dfbca4d051e5ad860239720816429a0a8e

tests/functional/check-outputs.nix

@@ -0,0 +1,25 @@
+with import ./config.nix;
+
+rec {
+  dep = import ./dependencies.nix {};
+
+  cycle = mkDerivation {
+    name = "cycle";
+    inherit dep;
+    outputs = [ "foo" "bar" "baz" ];
+    builder = builtins.toFile "builder.sh" ''
+      mkdir -p $foo/bin $bar/lib $baz/share
+      echo $bar > $foo/bin/alarm
+      echo $baz > $bar/lib/libfoo
+      echo $foo > $baz/share/lalala
+    '';
+  };
+
+  as_dependency = mkDerivation {
+    name = "depends-on-cycle";
+    inherit cycle;
+    builder = builtins.toFile "builder.sh" ''
+      touch $out
+    '';
+  };
+}

tests/functional/meson.build

@@ -173,6 +173,7 @@ functional_tests_scripts = [
   'regression-reference-checks.sh',
   'redirected-filter-source.sh',
   'daemon-trust.sh',
+  'output-cycles.sh',
 ]
 
 # Plugin tests require shared libraries support.

tests/functional/output-cycles.sh

@@ -0,0 +1,10 @@
+source common.sh
+
+clearStore
+
+(! nix-build check-outputs.nix -A cycle) 2>&1 | grepQuiet "cycle detected in build of '.*' in the references of output 'bar' from output 'foo'"
+
+error="$(! nix-build check-outputs.nix -A as_dependency 2>&1)"
+
+grepQuiet "cycle detected in build of '.*' in the references of output 'bar' from output 'foo'" <<<"$error"
+grepQuiet "error: 1 dependencies of derivation" <<<"$error"