Fix Platzhalter Editer im TemplateDesigner

LehrerApp.TemplateDesigner.Tests/ProjectLifecycleTests.cs

@@ -42,6 +42,42 @@ public sealed class ProjectLifecycleTests
         Assert.Equal("2026/27", manifest.Metadata["school-year"]);
     }
 
+    [Fact]
+    public void PlatzhalterAnlegen_WaehltIhnAusUndUebernimmtBearbeiteteDefinition()
+    {
+        var viewModel = new DesignerViewModel();
+        viewModel.Placeholders.Clear();
+
+        var placeholder = viewModel.AddPlaceholder();
+        placeholder.Name = "Sprache";
+        placeholder.Type = LehrerApp.Templating.PlaceholderType.Text;
+        placeholder.Required = true;
+        placeholder.Sample = "Deutsch";
+
+        Assert.Same(placeholder, viewModel.SelectedPlaceholder);
+        var definition = Assert.Single(viewModel.BuildManifest().Placeholders);
+        Assert.Equal("Sprache", definition.Name);
+        Assert.Equal(LehrerApp.Templating.PlaceholderType.Text, definition.Type);
+        Assert.True(definition.Required);
+
+        viewModel.RemoveSelectedPlaceholder();
+        Assert.Empty(viewModel.Placeholders);
+        Assert.Null(viewModel.SelectedPlaceholder);
+    }
+
+    [Fact]
+    public void DoppeltePlatzhalternamen_WerdenVerstaendlichAbgelehnt()
+    {
+        var viewModel = new DesignerViewModel();
+        viewModel.Placeholders.Clear();
+        viewModel.Placeholders.Add(new("Name", LehrerApp.Templating.PlaceholderType.Text, false, "A"));
+        viewModel.Placeholders.Add(new("Name", LehrerApp.Templating.PlaceholderType.Text, false, "B"));
+
+        var exception = Assert.Throws<InvalidDataException>(() => viewModel.BuildManifest());
+
+        Assert.Contains("mehrfach", exception.Message);
+    }
+
     private static readonly byte[] OnePixelPng = Convert.FromBase64String(
         "iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAQAAAC1HAwCAAAAC0lEQVR42mNk+A8AAQUBAScY42YAAAAASUVORK5CYII=");
 }