test-lib.lua: add support of default device selection

tests/scripts/scripts/lib/test-utils.lua

@@ -35,7 +35,6 @@ function u.createDeviceNode (name, media_class)
     u.lnkbls [name] = nil
     u.lnkbl_count = u.lnkbl_count + 1
   end)
-
   return node
 end
 
@@ -45,4 +44,48 @@ function u.createStreamNode (name)
   u.lnkbl_count = u.lnkbl_count + 1
 end
 
+u.metadata = cu.default_metadata_om:lookup ()
+assert (u.metadata ~= nil)
+
+-- hook to keep track of the linkables created.
+SimpleEventHook {
+  name = "test-utils-linking",
+  interests = {
+    -- on linkable added or removed, where linkable is adapter or plain node
+    EventInterest {
+      Constraint { "event.type", "=", "session-item-added" },
+      Constraint { "event.session-item.interface", "=", "linkable" },
+      Constraint { "item.factory.name", "c", "si-audio-adapter", "si-node" },
+    },
+  },
+  execute = function (event)
+    local lnkbl = event:get_subject ()
+    local lp = lnkbl.properties
+    local name = lp ["node.name"]
+
+    Log.info (lnkbl, "activated linkable: " .. name ..
+        " with media_class: " .. lp ["media.class"])
+    if not u.lnkbls [name] then
+      u.lnkbls [name] = lnkbl
+    else
+      Log.info ("unknown linkable " .. name)
+    end
+
+    if name == "default-device-node" then
+      local args = { ["name"] = name }
+      local args_json = Json.Object (args)
+      local key = nil
+
+      if lp ["media.class"] == "Audio/Sink" then
+        key = "default.configured.audio.sink"
+      elseif lp ["media.class"] == "Audio/Source" then
+        key = "default.configured.audio.source"
+      end
+
+      -- configure default device.
+      u.metadata:set (0, key, "Spa:String:JSON", args_json:get_data ())
+    end
+  end
+}:register ()
+
 return u