Preisrechner: Rappenrundung im Backend und Rabatt-Rechner im Web

agentd task d23b198e9bef4e0c99f52c532c317f70

tests/Prices.Tests/PriceCalculatorTests.cs

@@ -33,4 +33,31 @@ public sealed class PriceCalculatorTests
     {
         Assert.Throws<ArgumentOutOfRangeException>(() => PriceCalculator.ApplyDiscount(100m, 101m));
     }
-}
+
+    [Fact]
+    public void Swiss_rounding_example()
+    {
+        // 99.90 * 90 / 100 = 89.91, gerundet auf 0.05 = 89.90
+        Assert.Equal(89.90m, PriceCalculator.ApplyDiscount(99.90m, 10m));
+    }
+
+    [Fact]
+    public void Swiss_rounding_exact()
+    {
+        // 100.00 * 85 / 100 = 85.00, exakt ein 0.05-Vielfaches
+        Assert.Equal(85.00m, PriceCalculator.ApplyDiscount(100.00m, 15m));
+    }
+
+    [Fact]
+    public void Swiss_rounding_midpoint_up()
+    {
+        // 10.00 * 95 / 100 = 9.50, exakt
+        Assert.Equal(9.50m, PriceCalculator.ApplyDiscount(10.00m, 5m));
+    }
+
+    [Fact]
+    public void Negative_price_throws()
+    {
+        Assert.Throws<ArgumentOutOfRangeException>(() => PriceCalculator.ApplyDiscount(-1m, 10m));
+    }
+}