Method for the non-destructive testing of metal fusion welds on thin-walled pipes with a maximum wall thickness of 6 mm, wherein the method comprises the following steps: using a testing system having at least one test probe and at least one adjustment body which is made from a material which is the same or a material having at least approximately the same acoustic properties, and whose dimensions and the diameters/thicknesses of which are at least approximately the same as those of the respective pipe to be tested, wherein a plurality of blind holes are formed in the adjustment body, each with a different length/depth starting from their opening to their base, wherein the blind holes are aligned at an angle α relative to the surface of the adjustment body, and sound waves are coupled into the adjustment body at the same angle α, carrying out testing of a pipe and adjusting with the at least one test probe, wherein the test probe is a phased array sensor whose elements emitting and detecting sound waves are operated in a plurality of groups and the individual groups are each operated individually independently of one another so that sound waves are coupled in at several positions and at different angles from the surface of the respective pipe to be tested and the surface of the adjustment body and are thereby directed towards the welding seam of the pipe and during adjustment to the bottoms of blind holes (2.1, 2.2, 2.3), and the reflected sound waves are detected by this or another test probe and a comparison is made with the recorded measurement signal amplitude(s) to determine whether a predeterminable threshold value has been exceeded or not reached in order to detect a fault/defect, and a depth compensation curve is created for each group and each angle on the respective adjustment body so that a detected defect is always displayed with the same measurement signal level regardless of its depth position and the angle affecting it. using a testing system having at least one test probe and at least one adjustment body which is made from a material which is the same or a material having at least approximately the same acoustic properties, and whose dimensions and the diameters/thicknesses of which are at least approximately the same as those of the respective pipe to be tested, wherein a plurality of blind holes are formed in the adjustment body, each with a different length/depth starting from their opening to their base, wherein the blind holes are aligned at an angle α relative to the surface of the adjustment body, and sound waves are coupled into the adjustment body at the same angle α, carrying out testing of a pipe and adjusting with the at least one test probe, wherein the test probe is a phased array sensor whose elements emitting and detecting sound waves are operated in a plurality of groups and the individual groups are each operated individually independently of one another so that sound waves are coupled in at several positions and at different angles from the surface of the respective pipe to be tested and the surface of the adjustment body and are thereby directed towards the welding seam of the pipe and during adjustment to the bottoms of blind holes (2.1, 2.2, 2.3), and the reflected sound waves are detected by this or another test probe and a comparison is made with the recorded measurement signal amplitude(s) to determine whether a predeterminable threshold value has been exceeded or not reached in order to detect a fault/defect, and a depth compensation curve is created for each group and each angle on the respective adjustment body so that a detected defect is always displayed with the same measurement signal level regardless of its depth position and the angle affecting it.