strawberry: enable testing/checkPhase (#429449)

pkgs/by-name/st/strawberry/package.nix

@@ -31,6 +31,9 @@
   util-linux,
   sparsehash,
   rapidjson,
+
+  # tests
+  gtest,
 }:
 
 stdenv.mkDerivation (finalAttrs: {
@@ -99,6 +102,14 @@ stdenv.mkDerivation (finalAttrs: {
 
   cmakeFlags = [ (lib.cmakeBool "ENABLE_GPOD" false) ];
 
+  checkInputs = [ gtest ];
+  checkTarget = "strawberry_tests";
+  preCheck = ''
+    # defaults to "xcb" otherwise, which requires a display
+    export QT_QPA_PLATFORM=offscreen
+  '';
+  doCheck = true;
+
   postInstall = ''
     qtWrapperArgs+=(
       --prefix GST_PLUGIN_SYSTEM_PATH_1_0 : "$GST_PLUGIN_SYSTEM_PATH_1_0"