Yes, there are a couple of methods to test a fuel filter's functionality. The first was is called a 'Fuel Pressure Test'. This test checks the fuel pressure before and after the filter using a fuel pressure gauge. If the pressure is significantly lower than the recommended range, it may indicate a clogged or restricted fuel filter. The second method is a 'Flow Rate Test'. This test measures the flow rate of fuel passing through the filter by disconnecting the fuel line and directing it into a container. If the flow is weak or intermittent, it could suggest a restricted or clogged fuel filter.