extended PromptStreamExtensionsTests

Author: AndrewMorgan1

tests/PromptStream.AI.Tests/Extensions/PromptStreamExtensionsTests.cs

@@ -95,6 +95,20 @@ public void Methods_ShouldHandleEmptyStringsSafely()
             Assert.Empty(empty.ExtractPlaceholders());
             Assert.False(empty.HasUnresolvedPlaceholders());
         }
+
+        [Fact]
+        public void InterpolateVariables_ShouldReplaceNullValueWithEmptyString()
+        {
+            var text = "Hello {{name}}!";
+            var vars = new Dictionary<string, string?>
+            {
+                ["name"] = null
+            }!;
+
+            var result = text.InterpolateVariables(new Dictionary<string, string>(vars!));
+
+            Assert.Equal("Hello !", result);
+        }
     }
 }