Add unit tests for MergeHeaderMap method and update its behavior to handle overwrite conflicts

Fixed formatting issues

Added [JsonRequired] attribute.

Author: Jstatia

CoseSign1.Headers.Tests/Extensions/CoseHeaderExtensionsTests.cs

@@ -537,6 +537,71 @@ public void MergeHeaderMap_WithNullTargetMap_ShouldThrowArgumentNullException()
         Assert.Throws<ArgumentNullException>(() => targetMap!.MergeHeaderMap(sourceMap));
     }
 
+    [Test]
+    public void MergeHeaderMap_WithOverwriteConflictsFalse_ShouldPreserveTargetValues()
+    {
+        // Arrange
+        var targetMap = new CoseHeaderMap();
+        targetMap.Add(new CoseHeaderLabel("shared-key"), CoseHeaderValue.FromString("target-value"));
+        targetMap.Add(new CoseHeaderLabel("target-only"), CoseHeaderValue.FromInt32(100));
+
+        var sourceMap = new CoseHeaderMap();
+        sourceMap.Add(new CoseHeaderLabel("shared-key"), CoseHeaderValue.FromString("source-value"));
+        sourceMap.Add(new CoseHeaderLabel("source-only"), CoseHeaderValue.FromInt32(200));
+
+        // Act
+        CoseHeaderMap result = targetMap.MergeHeaderMap(sourceMap, overwriteConflicts: false);
+
+        // Assert
+        Assert.That(result, Is.SameAs(targetMap));
+        Assert.That(result.Count, Is.EqualTo(3));
+        Assert.That(result[new CoseHeaderLabel("shared-key")].GetValueAsString(), Is.EqualTo("target-value"));
+        Assert.That(result[new CoseHeaderLabel("target-only")].GetValueAsInt32(), Is.EqualTo(100));
+        Assert.That(result[new CoseHeaderLabel("source-only")].GetValueAsInt32(), Is.EqualTo(200));
+    }
+
+    [Test]
+    public void MergeHeaderMap_WithOverwriteConflictsTrue_ShouldReplaceTargetValues()
+    {
+        // Arrange
+        var targetMap = new CoseHeaderMap();
+        targetMap.Add(new CoseHeaderLabel("shared-key"), CoseHeaderValue.FromString("target-value"));
+        targetMap.Add(new CoseHeaderLabel("target-only"), CoseHeaderValue.FromInt32(100));
+
+        var sourceMap = new CoseHeaderMap();
+        sourceMap.Add(new CoseHeaderLabel("shared-key"), CoseHeaderValue.FromString("source-value"));
+        sourceMap.Add(new CoseHeaderLabel("source-only"), CoseHeaderValue.FromInt32(200));
+
+        // Act
+        CoseHeaderMap result = targetMap.MergeHeaderMap(sourceMap, overwriteConflicts: true);
+
+        // Assert
+        Assert.That(result, Is.SameAs(targetMap));
+        Assert.That(result.Count, Is.EqualTo(3));
+        Assert.That(result[new CoseHeaderLabel("shared-key")].GetValueAsString(), Is.EqualTo("source-value"));
+        Assert.That(result[new CoseHeaderLabel("target-only")].GetValueAsInt32(), Is.EqualTo(100));
+        Assert.That(result[new CoseHeaderLabel("source-only")].GetValueAsInt32(), Is.EqualTo(200));
+    }
+
+    [Test]
+    public void MergeHeaderMap_WithDefaultParameter_ShouldOverwriteConflicts()
+    {
+        // Arrange
+        var targetMap = new CoseHeaderMap();
+        targetMap.Add(new CoseHeaderLabel("key"), CoseHeaderValue.FromString("target-value"));
+
+        var sourceMap = new CoseHeaderMap();
+        sourceMap.Add(new CoseHeaderLabel("key"), CoseHeaderValue.FromString("source-value"));
+
+        // Act - Using default parameter (should overwrite)
+        CoseHeaderMap result = targetMap.MergeHeaderMap(sourceMap);
+
+        // Assert
+        Assert.That(result, Is.SameAs(targetMap));
+        Assert.That(result.Count, Is.EqualTo(1));
+        Assert.That(result[new CoseHeaderLabel("key")].GetValueAsString(), Is.EqualTo("source-value"));
+    }
+
     [Test]
     public void ToCoseHeaderMap_WithHeadersContainingNullLabel_ShouldSkipThem()
     {

CoseSign1.Headers/Extensions/CoseHeaderExtensions.cs

@@ -76,9 +76,18 @@ public static CoseHeaderMap ToCoseHeaderMap<T>(this IEnumerable<CoseHeader<T>> h
     /// </summary>
     /// <param name="targetMap">The target map to merge into.</param>
     /// <param name="sourceMap">The source map to merge from. If null, returns the target map unchanged.</param>
+    /// <param name="overwriteConflicts">
+    /// If true (default), source map values will overwrite target map values when keys conflict.
+    /// If false, existing target map values are preserved and conflicting source values are ignored.
+    /// </param>
     /// <returns>The target map with merged headers.</returns>
+    /// <remarks>
+    /// When <paramref name="overwriteConflicts"/> is true, any header keys that exist in both maps
+    /// will have their values replaced by the source map values. When false, the target map values
+    /// are preserved and the conflicting source values are silently ignored.
+    /// </remarks>
     /// <exception cref="ArgumentNullException">Thrown when targetMap is null.</exception>
-    public static CoseHeaderMap MergeHeaderMap(this CoseHeaderMap targetMap, CoseHeaderMap? sourceMap)
+    public static CoseHeaderMap MergeHeaderMap(this CoseHeaderMap targetMap, CoseHeaderMap? sourceMap, bool overwriteConflicts = true)
     {
         if (targetMap == null)
         {
@@ -92,7 +101,10 @@ public static CoseHeaderMap MergeHeaderMap(this CoseHeaderMap targetMap, CoseHea
 
         foreach (var kvp in sourceMap)
         {
-            targetMap[kvp.Key] = kvp.Value;
+            if (overwriteConflicts || !targetMap.ContainsKey(kvp.Key))
+            {
+                targetMap[kvp.Key] = kvp.Value;
+            }
         }
 
         return targetMap;

CoseSign1.Headers/Local/CoseHeader.cs

@@ -12,12 +12,14 @@ public class CoseHeader<TypeV>
     /// <summary>
     /// Gets or sets the Header label.
     /// </summary>
+    [JsonRequired]
     [JsonPropertyName("label")]
     public string Label { get; set; }
 
     /// <summary>
     /// Gets or sets the Header value.
     /// </summary>
+    [JsonRequired]
     [JsonPropertyName("value")]
     public TypeV Value { get; set; }