A method of testing a display having a plurality of backlights, the method comprising: capturing signals (2.1) provided by a sensor to obtain information of a colour of a sequence of colours displayed by the display at a location of an identifier displayed with each frame of a sequence of frames, in which the colour of the identifier of at least each three frames of the sequence of frames differs from each other; analysing the captured signals; determining colours of the identifier using samples taken from the captured signals; using information on a switching of the determined colours to determine a change of a frame in the sequence of frames displayed by the display; and using the determined change of frame to further: determine timestamps of frames and frame times in the sequence of frames displayed by the display; and to determine whether one or more frames of the sequence of frames were not displayed by the display by comparing each determined colour to an expected colour of the sequence of colours, characterised in that the analysing of the captured signals for the determination of frames not displayed comprises: using two or more samples taken from the signals from the sensor to detect rising and falling edges of each signal, said rising and falling edges indicating changes of illumination level of a backlight; using the detected rising and falling edges to determine the time for which the backlight is switched on, the determined time representing an illumination period of the backlight; and using the determined backlight illumination periods for providing timing information to synchronize sampling of the colour of the identifier to the backlight illumination periods for the determining of each individual colour of the sequence of colours. capturing signals (2.1) provided by a sensor to obtain information of a colour of a sequence of colours displayed by the display at a location of an identifier displayed with each frame of a sequence of frames, in which the colour of the identifier of at least each three frames of the sequence of frames differs from each other; analysing the captured signals; determining colours of the identifier using samples taken from the captured signals; using information on a switching of the determined colours to determine a change of a frame in the sequence of frames displayed by the display; and using the determined change of frame to further: determine timestamps of frames and frame times in the sequence of frames displayed by the display; and to determine whether one or more frames of the sequence of frames were not displayed by the display by comparing each determined colour to an expected colour of the sequence of colours, determine timestamps of frames and frame times in the sequence of frames displayed by the display; and to determine whether one or more frames of the sequence of frames were not displayed by the display by comparing each determined colour to an expected colour of the sequence of colours, characterised in that the analysing of the captured signals for the determination of frames not displayed comprises: using two or more samples taken from the signals from the sensor to detect rising and falling edges of each signal, said rising and falling edges indicating changes of illumination level of a backlight; using the detected rising and falling edges to determine the time for which the backlight is switched on, the determined time representing an illumination period of the backlight; and using the determined backlight illumination periods for providing timing information to synchronize sampling of the colour of the identifier to the backlight illumination periods for the determining of each individual colour of the sequence of colours. using two or more samples taken from the signals from the sensor to detect rising and falling edges of each signal, said rising and falling edges indicating changes of illumination level of a backlight; using the detected rising and falling edges to determine the time for which the backlight is switched on, the determined time representing an illumination period of the backlight; and using the determined backlight illumination periods for providing timing information to synchronize sampling of the colour of the identifier to the backlight illumination periods for the determining of each individual colour of the sequence of colours.