xs = randn(10)

d = Affine(10, 20)

@test d(xs) ≈ (xs'*d.W.x + d.b.x)[1,:]

let
  @capture(syntax(d), _Frame(_Line(x_[1] * W_ + b_)))
  @test isa(x, Input) && isa(W, Param) && isa(b, Param)
end