added tests for SDEFunctionExpr

Signed-off-by: sivasathyaseeelan <[email protected]>

Author: sivasathyaseeelan

test/sdesystem.jl

@@ -868,3 +868,55 @@ end
     @test length(ModelingToolkit.get_noiseeqs(sys)) == 1
     @test length(observed(sys)) == 1
 end
+
+@testset "SDEFunctionExpr" begin
+    @parameters σ ρ β
+    @variables x(tt) y(tt) z(tt)
+
+    eqs = [D(x) ~ σ * (y - x),
+        D(y) ~ x * (ρ - z) - y,
+        D(z) ~ x * y - β * z]
+
+    noiseeqs = [0.1 * x,
+        0.1 * y,
+        0.1 * z]
+
+    @named sys = ODESystem(eqs, tt, [x, y, z], [σ, ρ, β])
+    
+    @named de = SDESystem(eqs, noiseeqs, tt, [x, y, z], [σ, ρ, β], tspan = (0.0, 10.0))
+    de = complete(de)
+    
+    f = SDEFunctionExpr(de)
+    @test f isa Expr
+
+    @testset "Configuration Tests" begin
+        # Test with `tgrad`
+        f_tgrad = SDEFunctionExpr(de; tgrad = true)
+        @test f_tgrad isa Expr
+
+        # Test with `jac`
+        f_jac = SDEFunctionExpr(de; jac = true)
+        @test f_jac isa Expr
+
+        # Test with sparse Jacobian
+        f_sparse = SDEFunctionExpr(de; sparse = true)
+        @test f_sparse isa Expr
+    end
+
+    @testset "Mass Matrix Handling" begin
+        # Test with default mass matrix
+        @test eval(SDEFunctionExpr(de).args[7]) == UniformScaling{Bool}(true)
+
+        # Test with non-trivial mass matrix
+        u0 = [1.0, 2.0, 3.0]
+        f_mass = SDEFunctionExpr(de, u0 = u0)
+        @test f_mass isa Expr
+    end
+
+    @testset "Ordering Tests" begin
+        dvs = [z, y, x]
+        ps = [β, ρ, σ]
+        f_order = SDEFunctionExpr(de, dvs, ps)
+        @test f_order isa Expr
+    end
+end