add test for strip_solution interpolation

Author: jClugstor

test/downstream/ode_stripping.jl

@@ -5,4 +5,6 @@ tspan = (0.0, 1.0)
 prob = ODEProblem(f, u0, tspan)
 sol = solve(prob, Tsit5(), reltol = 1e-8, abstol = 1e-8)
 
-@test isnothing(strip_solution(sol).f)
+@test isnothing(strip_solution(sol).f)
+
+@test isnothing(strip_solution(sol).interp.f)