test: update serialization tests

Author: AayushSabharwal

test/serialization.jl

@@ -8,8 +8,8 @@ sys = complete(sys)
 for prob in [
     eval(ModelingToolkit.ODEProblem{false}(sys, nothing, nothing,
         SciMLBase.NullParameters())),
-    eval(ModelingToolkit.ODEProblemExpr{false}(sys, nothing, nothing,
-        SciMLBase.NullParameters()))
+    eval(ModelingToolkit.ODEProblem{false}(sys, nothing, nothing,
+        SciMLBase.NullParameters(); expression = Val{true}))
 ]
     _fn = tempname()
 
@@ -47,26 +47,8 @@ sol_ = solve(prob_, ImplicitEuler())
 ## Check ODEProblemExpr with Observables -----------
 
 # build the observable function expression
-obs_exps = []
-for var in all_obs
-    f = ModelingToolkit.build_explicit_observed_function(ss, var; expression = true)
-    sym = ModelingToolkit.getname(var) |> string
-    ex = :(if name == Symbol($sym)
-        return $f(u0, p, t)
-    end)
-    push!(obs_exps, ex)
-end
-# observedfun expression for ODEFunctionExpr
-observedfun_exp = :(function obs(var, u0, p, t)
-    if var isa AbstractArray
-        return obs.(var, (u0,), (p,), (t,))
-    end
-    name = ModelingToolkit.getname(var)
-    $(obs_exps...)
-end)
-
 # ODEProblemExpr with observedfun_exp included
-probexpr = ODEProblemExpr{true}(ss, [capacitor.v => 0.0], (0, 0.1); observedfun_exp);
+probexpr = ODEProblem{true}(ss, [capacitor.v => 0.0], (0, 0.1); expr = Val{true});
 prob_obs = eval(probexpr)
 sol_obs = solve(prob_obs, ImplicitEuler())
 @show all_obs