Methods and systems for testing a subterranean formation penetrated by a wellbore are provided. A testing tool has a plurality of packers spaced apart along the axis of the tool, and at least a testing port. The testing tool is positioned into the wellbore and packers are extended into sealing engagement with the wellbore wall, sealing thereby an interval of the wellbore. In some embodiments, the wellbore interval sealed between two packers is adjusted downhole. In one embodiment, the location of the testing port is adjusted between two packers. The methods may be used to advantage for reducing the contamination of the formation fluid by fluids or debris in the wellbore.