added argument validation to WmiAssert

WmiLight.UnitTests/Helpers/WmiAssert.cs

@@ -7,6 +7,21 @@ internal static class WmiAssert
     {
         internal static void AreEqual<T>(ManagementBaseObject msObject, WmiObject wmiObject, string propertyName)
         {
+            if (msObject is null)
+            {
+                throw new ArgumentNullException(nameof(msObject));
+            }
+
+            if (wmiObject is null)
+            {
+                throw new ArgumentNullException(nameof(wmiObject));
+            }
+
+            if (string.IsNullOrEmpty(propertyName))
+            {
+                throw new ArgumentException($"'{nameof(propertyName)}' cannot be null or empty.", nameof(propertyName));
+            }
+
             if (typeof(T).IsArray)
             {
                 CollectionAssert.AreEqual((T)msObject.GetPropertyValue(propertyName) as ICollection, wmiObject.GetPropertyValue<T>(propertyName) as ICollection);