Add MapMerge

struct_test.go

@@ -94,8 +94,6 @@ func TestStructToMapRecursive(t *testing.T) {
     default:
       t.Fatal("is not map")
   }
-
-
 }
 
 func TestMapToStruct(t *testing.T) {
@@ -267,7 +265,6 @@ func TestStructHasBsonName_False(t *testing.T) {
 }
 
 func TestCopyMatching(t *testing.T) {
-
   type O struct {
     Name string
     Age int
@@ -293,5 +290,21 @@ func TestCopyMatching(t *testing.T) {
   if to.Name != "Nick" && to.Age != 15 && to.Active != true {
     t.Fatalf("Failed to copy matching fields to %v", to)
   }
-
 }
+
+func TestMapMerge(t *testing.T) {
+  m1 := map[string]any{
+    "a": "va",
+    "b": "vb",
+  }
+  m2 := map[string]any{
+    "c": "vc",
+    "d": "vd",
+  }
+
+  m := MapMerge(m1, m2)
+
+  if len(m) != 4 {
+    t.Fatalf("Merged map should have lenght 4 not %d", len(m))
+  }
+}