A test for correctness of line-shape theories is devised for the near-line-center shape. The test is insensitive to variation in any parameter such as line strength, line width, water vapor continuum absorption, or oxygen absorption. The absorption data for the 22-GHz water vapor line obtained by Becker and Autler clearly agree with the absorption line shape derived by Van Vleck and Weisskopf, and their data rule out the Gross and full Lorentz line shapes. Properties of the three line shapes are discussed. Further experimentation is suggested.