A testing system for verifying the integrity of a flexible bag , using a gas tracer, comprising: - an enclosure delimiting a vacuum chamber (CH) in which an internal volume is fluid-tightly isolated from outside of the enclosure in an operating configuration of the enclosure; - a first helium supplying device provided with a feeding pipe for filling the flexible bag at a filling step with helium, via an outlet of the feeding pipe when the flexible bag is placed in the vacuum chamber (CH) so as to be surrounded by the internal volume ; - a vacuum suction assembly (P1, P3) for performing vacuum suction and extracting gas from the internal volume outside the flexible bag , in a suction mode; - at least one pressure measurement member for detecting helium partial pressure in a detection area of the internal volume , the detection area communicating with a suction inlet of the vacuum suction assembly (P1, P3); - at least one source of pressurized helium intended to be introduced inside the flexible bag ; characterized in that the testing system further comprises: - a second helium supplying device for adding helium in the internal volume outside the flexible bag , the second helium supplying device comprising a feeding member that is: - distinct from the feeding pipe , - communicating with a gas source; - a control unit for controlling the first helium supplying device and the second helium supplying device , and adapted to trigger the second helium supplying device before the first helium supplying device ; - an analysis module using information representative of evolution over time of helium partial pressure detected by the pressure measurement member before and after the filling step, the analysis module being configured to detect a helium leak on the basis of said information. - an enclosure delimiting a vacuum chamber (CH) in which an internal volume is fluid-tightly isolated from outside of the enclosure in an operating configuration of the enclosure; - a first helium supplying device provided with a feeding pipe for filling the flexible bag at a filling step with helium, via an outlet of the feeding pipe when the flexible bag is placed in the vacuum chamber (CH) so as to be surrounded by the internal volume ; - a vacuum suction assembly (P1, P3) for performing vacuum suction and extracting gas from the internal volume outside the flexible bag , in a suction mode; - at least one pressure measurement member for detecting helium partial pressure in a detection area of the internal volume , the detection area communicating with a suction inlet of the vacuum suction assembly (P1, P3); - at least one source of pressurized helium intended to be introduced inside the flexible bag ; - a second helium supplying device for adding helium in the internal volume outside the flexible bag , the second helium supplying device comprising a feeding member that is: - distinct from the feeding pipe , - communicating with a gas source; - distinct from the feeding pipe , - communicating with a gas source; - a control unit for controlling the first helium supplying device and the second helium supplying device , and adapted to trigger the second helium supplying device before the first helium supplying device ; - an analysis module using information representative of evolution over time of helium partial pressure detected by the pressure measurement member before and after the filling step, the analysis module being configured to detect a helium leak on the basis of said information. <EOS>