Added PowerPoint templates to the Slide Assistant (#1055)

Co-authored-by: Thorsten Sommer <SommerEngineering@users.noreply.github.com>

app/Tests/Tools/PowerPoint/StreamedSlideCounterTests.cs

@@ -0,0 +1,57 @@
+using AIStudio.Tools.PowerPoint;
+
+namespace AIStudio.Tests.Tools.PowerPoint;
+
+/// <summary>
+/// Checks how the slides of an answer are counted while it streams in.
+/// </summary>
+[TestFixture]
+public sealed class StreamedSlideCounterTests
+{
+    private const string ANSWER = """{"title": "Deck", "slides": [{"layout": "L1", "title": "Start"}, {"template_slide": 2}, {"layout": "L3", "title": "Results", "texts": [["All \"layout\" keys"]]}]}""";
+
+    [Test]
+    public void SlidesOnLayoutsAndTemplateSlidesAreCounted()
+    {
+        Assert.That(new StreamedSlideCounter().Count(ANSWER), Is.EqualTo(3), "An escaped key within a text does not start a slide.");
+    }
+
+    [Test]
+    public void EverySplitOfTheStreamGivesTheSameCount()
+    {
+        //
+        // Wherever the chunks end, a key cut in two by them is counted once, and only once
+        // it is complete:
+        //
+        for (var chunkLength = 1; chunkLength <= 20; chunkLength++)
+        {
+            var counter = new StreamedSlideCounter();
+            var count = 0;
+            for (var end = chunkLength; end < ANSWER.Length + chunkLength; end += chunkLength)
+                count = counter.Count(ANSWER[..Math.Min(end, ANSWER.Length)]);
+
+            Assert.That(count, Is.EqualTo(3), $"Chunks of {chunkLength} characters");
+        }
+    }
+
+    [Test]
+    public void AKeyCountsOnlyOnceItIsComplete()
+    {
+        var counter = new StreamedSlideCounter();
+        Assert.Multiple(() =>
+        {
+            Assert.That(counter.Count("""{"slides": [{"lay"""), Is.Zero);
+            Assert.That(counter.Count("""{"slides": [{"layout"""), Is.Zero, "The closing quotation mark is still missing.");
+            Assert.That(counter.Count("""{"slides": [{"layout": "L1"}"""), Is.EqualTo(1));
+        });
+    }
+
+    [Test]
+    public void AShorterAnswerIsCountedAnew()
+    {
+        var counter = new StreamedSlideCounter();
+        counter.Count(ANSWER);
+
+        Assert.That(counter.Count("""{"slides": [{"layout": "L1"}"""), Is.EqualTo(1));
+    }
+}