add test

Author: lxvm

test/lib/lib.jl

@@ -4,5 +4,6 @@
         t2 = (a=1, b=2)
         @test Zygote.accum(t1, t2) == (a = 2, b = 4, c = 3)
         @test_throws ArgumentError Zygote.accum(t2, t1)
+        @test Zygote.accum(fill(0.0), fill(0.0)) == fill(0.0)
     end
 end