add test for 1x1 svector

Author: Langwen Huang

test/test_ad.jl

@@ -218,4 +218,10 @@ J = forwarddiff_color_jacobian(oopf,x)
 @test J ≈ Matrix(I,4,4)
 J = zero(J)
 forwarddiff_color_jacobian!(J,iipf,x,dx=similar(x))
-@test J ≈ Matrix(I,4,4)
+@test J ≈ Matrix(I,4,4)
+
+#1x1 SVector test
+x = SVector{1}([1.])
+f(x) = x
+J = forwarddiff_color_jacobian(f,x)
+@test J ≈ SMatrix{1,1}([1.])