Actually fix all tests

src/derivatives.jl

@@ -71,11 +71,6 @@ function _derivative(A::SmoothedConstantInterpolation{<:AbstractVector}, t::Numb
     idx = get_idx(A, t, iguess)
     d_lower, d_upper, c_lower, c_upper = get_parameters(A, idx)
 
-    # Fix extrapolation behavior as constant for now
-    if t <= first(A.t) || t >= last(A.t)
-        return zero(c_upper / oneunit(t))
-    end
-
     if (t - A.t[idx]) < d_lower
         -2c_lower * ((t - A.t[idx]) / d_lower - 1) / d_lower
     elseif (A.t[idx + 1] - t) < d_upper

src/parameter_caches.jl

@@ -54,13 +54,11 @@ function smoothed_constant_interpolation_parameters(
     if isone(idx) || (idx == length(t))
         # If extrapolation is periodic, make the transition differentiable
         if extrapolation_left == extrapolation_right == ExtrapolationType.Periodic
-            if isone(idx)
-                min(t[end] - t[end - 1], t[2] - t[1], 2d_max) / 2, (u[1] - u[end - 1]) / 2
-            else
-                min(t[end] - t[end - 1], t[2] - t[1], 2d_max) / 2, (u[1] - u[end - 1]) / 2
-            end
+            min(t[end] - t[end - 1], t[2] - t[1], 2d_max) / 2, (u[1] - u[end - 1]) / 2
         else
-            zero(one(eltype(t)) / 2), zero(one(eltype(u)) / 2)
+            d = isone(idx) ? min(t[2] - t[1], 2d_max) / 2 :
+                min(t[end] - t[end - 1], 2d_max) / 2
+            d, zero(one(eltype(u)) / 2)
         end
     else
         min(t[idx] - t[idx - 1], t[idx + 1] - t[idx], 2d_max) / 2, (u[idx] - u[idx - 1]) / 2