  We consider a regression model with errors that are a.s. negative. Thus the
regression function is not the expected value of the observations but the right
endpoint of their support. We develop two goodness-of-fit tests for the
hypotheses that the regression function is an affine function, study the
asymptotic distributions of the test statistics in order to approximately fix
the sizes of the tests, derive their finite-sample properties based on
simulations and apply them to life expectancy data.
