public void ReturnNullIfEntityNull()
{
IMdmEntity value = null;
var candidate = value.SystemId();
Assert.IsNull(candidate);
}
/// <summary>
/// Gets an identifier value for a system
/// </summary>
/// <param name="entity">Entity to use</param>
/// <param name="systemName">System to check</param>
/// <returns>First identifier found for the system or <see cref="string.Empty"/> if not found.</returns>
public static string SystemIdentifier(this IMdmEntity entity, string systemName = "Nexus")
{
var id = entity.SystemId(systemName);
return(id == null ? null : id.Identifier);
}