1. A method for inspecting an entity comprising a liquid-filled container for one or more test parameters of the liquid, the container, or both, wherein the entity is irradiated by irradiating means, rotated and axially line scanned along a line parallel with the axis of rotation by detecting means detecting radiation reflected, diffracted, or scattered from the entity, the inspection comprising at least one sequence of: a) rotating the entity according to a predetermined rate profile having one or more periods of constant angular velocities, line scanning the container axially during the periods of constant angular velocities, and comparing pixel values of said line scans with set references; and b) rotating the entity according to a predetermined rate profile comprising rates of rotation causing the liquid to circulate and foreign bodies having densities higher than the liquid to accumulate at the container wall, bringing the container to a standstill with the liquid rotating, line scanning the entity axially before the rotation of the liquid is substantially reduced, digitally filtering the pixel values of said line scans, and comparing the filtered values with predetermined references.