A test arrangement for fatigue testing a wind turbine blade, including a floor-mounted test rig having a fixing device for fixing the wind turbine blade to the test rig and an excitation assembly for exciting the wind turbine blade at a test frequency, wherein the test rig includes a liquid tank having a chamber containing a predefined liquid, wherein the liquid in the liquid tank has a resonance frequency depending on the amount of liquid in the liquid tank and the chamber geometry is provided.