As a convenient shorthand, test also allows you to specify equality for multiple expressions; for
example, test x1+x2 = x3+x4 = x5+x6 tests that the three specified pairwise sums of coefficients
are equal.

Stata’s ability to simplify and test complex hypotheses is limited to linear hypotheses. If you
attempt to test a nonlinear hypothesis, you will be told that it is not possible:
. test 2.region/3.region=2.region
+3
.region
not possible with test
r(131);

The real power of test is demonstrated when we test joint hypotheses. Perhaps we wish to test
whether the region variables, taken as a whole, are significant by testing whether the coefficients on
2.region, 3.region, and 4.region are simultaneously zero. test allows us to specify multiple
conditions to be tested, each embedded within parentheses.