Add test for merging Pow's

Author: Suavesito-Olimpiada

test/basics.jl

@@ -195,5 +195,6 @@ end
         @test x - x === 0
         @test isequal(-x, -1x)
         @test isequal(x^1, x)
+        @test isequal((x^-1)*inv(x^-1), 1)
     end
 end