New rapid methods for testing oilwells are presented based on modified closed chamber theory. The tests are of great assistance in solving pumping problems. In the case of a sudden drop in production, the tests define the problem in real time. Tubing leaks, pump failure, defective check valve or flowline failure can readily be detected at the time of the test and remedied in a cost effective manner The tests are of short duration (twenty minutes or less). They have minimum equipment requirements (i.e., a critical flow prover, a high-resolution pressure recorder and a laptop computer). Several tests can be conducted in a single day, travel time included. The mass balance theory and relevant equations behind these tests an developed and explained with emphasis on the practical aspects. Test procedures are described with step by step detail in field examples. One of these examples obviated the need for a previously ordered service rig. Another example shows how a simple, non-quantitative visual scan of the pressure response can be used to immediately recognize problems (in this case the problem was a severe foam buildup). Some other applications of the method are mentioned, including gas well testing, workover and completions, surface casing vent tests and nitrogen cushion drill stem tests.