add test, fix

Author: vyudu

src/systems/diffeqs/sdesystem.jl

@@ -768,11 +768,7 @@ function DiffEqBase.SDEProblem{iip, specialize}(
         noise_rate_prototype = noise_rate_prototype, kwargs...)
 end
 
-function DiffEqBase.SDEProblem{iip, specialize}(
-        sys::ODESystem, u0map = [], tspan = get_tspan(sys),
-        parammap = DiffEqBase.NullParameters();
-        sparsenoise = nothing, check_length = true,
-        callback = nothing, kwargs...) where {iip, specialize}
+function DiffEqBase.SDEProblem(sys::ODESystem, args...; kwargs...)
 
     if any(ModelingToolkit.isbrownian, unknowns(sys))
         error("SDESystem constructed by defining Brownian variables with @brownian must be simplified by calling `structural_simplify` before a SDEProblem can be constructed.")

test/sdesystem.jl

@@ -868,3 +868,24 @@ end
     @test length(ModelingToolkit.get_noiseeqs(sys)) == 1
     @test length(observed(sys)) == 1
 end
+using ModelingToolkit, StochasticDiffEq
+using ModelingToolkit: t_nounits as t, D_nounits as D
+
+@testset "Error when constructing SDESystem without `structural_simplify`" begin
+    @parameters σ ρ β
+    @variables x(t) y(t) z(t)
+    @brownian a
+    eqs = [D(x) ~ σ * (y - x) + 0.1a * x,
+        D(y) ~ x * (ρ - z) - y + 0.1a * y,
+        D(z) ~ x * y - β * z + 0.1a * z]
+
+    @named de = System(eqs, t)
+    de = complete(de)
+
+    u0map = [x => 1.0, y => 0.0, z => 0.0]
+    parammap = [σ => 10.0, β => 26.0, ρ => 2.33]
+
+    @test_throws ErrorException("SDESystem constructed by defining Brownian variables with @brownian must be simplified by calling `structural_simplify` before a SDEProblem can be constructed.") SDEProblem(de, u0map, (0.0, 100.0), parammap)
+    de = structural_simplify(de)
+    @test SDEProblem(de, u0map, (0.0, 100.0), parammap) isa SDEProblem
+end