Method for operating and testing a light detection and ranging system, particularly for safety relevant applications, comprising alternating operating and testing cycles, wherein the operating cycle comprises the steps of: sending a light signal from at least one first light source to the surroundings of the light detection and ranging system; receiving a light signal from the surroundings of the light detection and ranging system by at least one photo detector; processing the signal of the at least one photo detector for detecting objects in the surroundings of the light detection and ranging system by a signal processing unit; controlling, particularly synchronizing, the sending of the light signal and receiving of the light signal by a control unit; and wherein the testing cycle comprises the steps of: sending a test light signal within the light detection and ranging system to the at least one photo detector by a second light source of a test unit; receiving the test light signal from the second light source of the test unit by the at least one photo detector; processing the signal of the at least one photo detector by the signal processing unit; comparing the signal of the signal processing unit with an expected signal based on the test light signal for testing the light detection and ranging system, characterized in that the test light signal is generated by a test light signal generating unit, wherein the test light signal generating unit can generate specific test light signals with different waveforms and wavelength designed to test specific functions of the light detection and ranging system. sending a light signal from at least one first light source to the surroundings of the light detection and ranging system; receiving a light signal from the surroundings of the light detection and ranging system by at least one photo detector; processing the signal of the at least one photo detector for detecting objects in the surroundings of the light detection and ranging system by a signal processing unit; controlling, particularly synchronizing, the sending of the light signal and receiving of the light signal by a control unit; and wherein the testing cycle comprises the steps of: sending a test light signal within the light detection and ranging system to the at least one photo detector by a second light source of a test unit; receiving the test light signal from the second light source of the test unit by the at least one photo detector; processing the signal of the at least one photo detector by the signal processing unit; comparing the signal of the signal processing unit with an expected signal based on the test light signal for testing the light detection and ranging system, characterized in that the test light signal is generated by a test light signal generating unit, wherein the test light signal generating unit can generate specific test light signals with different waveforms and wavelength designed to test specific functions of the light detection and ranging system. sending a test light signal within the light detection and ranging system to the at least one photo detector by a second light source of a test unit; receiving the test light signal from the second light source of the test unit by the at least one photo detector; processing the signal of the at least one photo detector by the signal processing unit; comparing the signal of the signal processing unit with an expected signal based on the test light signal for testing the light detection and ranging system, characterized in that the test light signal is generated by a test light signal generating unit, wherein the test light signal generating unit can generate specific test light signals with different waveforms and wavelength designed to test specific functions of the light detection and ranging system.