test(plugins): verify yaegi plugin event listener registration

Init() succeeds without panics, meaning events.RegisterListener
accepted the interpreted Listener type across the yaegi boundary.

pkg/plugins/yaegi/events_test.go

@@ -0,0 +1,48 @@
+// Vikunja is a to-do list application to facilitate your life.
+// Copyright 2018-present Vikunja and contributors. All rights reserved.
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+package yaegi
+
+import (
+	"testing"
+
+	"code.vikunja.io/api/pkg/log"
+)
+
+func TestPluginEventListener(t *testing.T) {
+	log.InitLogger()
+
+	loaded, err := LoadPluginFull(examplePluginDir)
+	if err != nil {
+		t.Fatalf("LoadPluginFull failed: %v", err)
+	}
+
+	// Call Init() — this registers the TestListener for TaskCreatedEvent.
+	// If the Listener interface boundary is broken, this will panic with a
+	// reflection error when calling events.RegisterListener.
+	err = loaded.Plugin.Init()
+	if err != nil {
+		t.Fatalf("plugin Init failed: %v", err)
+	}
+	t.Log("Init() succeeded — events.RegisterListener accepted the interpreted Listener")
+
+	// Verify Shutdown works too
+	err = loaded.Plugin.Shutdown()
+	if err != nil {
+		t.Fatalf("plugin Shutdown failed: %v", err)
+	}
+	t.Log("Shutdown() succeeded")
+}