1. A method for testing a well using a retrievable downhole testing tool adapted to be temporarily installed in the well, the retrievable downhole testing tool comprising a variable choke, at least two measuring sensors, and a tool control unit adapted to control the variable choke and to process information from the measuring sensors, the at least two measuring sensors being adapted to measure physical parameters including pressure, whereby at least one measuring sensor is situated above the variable choke, and at least one measuring sensor is situated below the variable choke, the method comprising: pre-programming the retrievable downhole testing tool with a specified test sequence for controlling a downhole flow rate using the variable choke and for executing downhole measurements of physical parameters at specified flow periods using the measuring sensors; temporarily installing the retrievable downhole testing tool in the well; initiating the specified test sequence; and adapting the specified test sequence according to a pre-defined stability criterion using the tool control unit.