/// <summary>
/// Adds a test filter if not already added.
/// </summary>
/// <param name="filter">The filter to add.</param>
/// <exception cref="ArgumentNullException">Thrown if <paramref name="filter"/> is null.</exception>
public void AddTestFilter(FilterInfo filter)
{
if (filter == null)
throw new ArgumentNullException("filter");
filter.Validate();
if (!testFilters.Contains(filter))
testFilters.Add(filter);
}
