adds test

Author: ValentinKaisermayer

test/odesystem.jl

@@ -250,6 +250,30 @@ sol_dpmap = solve(prob_dpmap, Rodas5())
 
 @test sol_pmap.u ≈ sol_dpmap.u
 
+@testset "symbolic remake with nested system" begin
+    function makesys(name)
+        @parameters t a=1.0
+        @variables x(t) = 0.0
+        D = Differential(t)
+        ODESystem([D(x) ~ -a * x]; name)
+    end
+
+    function makecombinedsys()
+        sys1 = makesys(:sys1)
+        sys2 = makesys(:sys2)
+        @parameters t b=1.0
+        ODESystem(Equation[], t, [], [b]; systems = [sys1, sys2], name = :foo)
+    end
+
+    sys = makecombinedsys()
+    @unpack sys1, b = sys
+    prob = ODEProblem(sys, Pair[])
+    prob_new = SciMLBase.remake(prob, p = Dict(sys1.a => 3.0, b => 4.0),
+                                u0 = Dict(sys1.x => 1.0))
+    @test prob_new.p == [4.0, 3.0, 1.0]
+    @test prob_new.u0 == [1.0, 0.0]
+end
+
 # test kwargs
 prob2 = ODEProblem(sys, u0, tspan, p, jac = true)
 prob3 = ODEProblem(sys, u0, tspan, p, jac = true, sparse = true) #SparseMatrixCSC need to handle