diff --git a/Project.toml b/Project.toml
index 5530fed32..a46d712d9 100644
--- a/Project.toml
+++ b/Project.toml
@@ -36,8 +36,9 @@ TreeViews = "0.3"
 julia = "1.2"
 
 [extras]
+Pkg = "44cfe95a-1eb2-52ea-b672-e2afdf69b78f"
 SafeTestsets = "1bc83da4-3b8d-516f-aca4-4fe02f6d838f"
 Test = "8dfed614-e22c-5e08-85e1-65c5234f0b40"
 
 [targets]
-test = ["Test", "SafeTestsets"]
+test = ["Test", "SafeTestsets", "Pkg"]
diff --git a/test/array.jl b/test/overloads.jl
similarity index 51%
rename from test/array.jl
rename to test/overloads.jl
index 93cb577f0..656991d24 100644
--- a/test/array.jl
+++ b/test/overloads.jl
@@ -1,9 +1,8 @@
-using Symbolics
+using ModelingToolkit
 using LinearAlgebra
 using SparseArrays: sparse
 using Test
 
-
 @variables a,b,c,d,e,f,g,h,i
 
 # test hashing
@@ -14,6 +13,10 @@ aa = a; # old a
 @test isequal(a, aa)
 @test hash(a) == hash(aa)
 
+@test isequal(get_variables(a+aa+1), [a])
+
+@test hash(a+b ~ c+d) == hash(a+b ~ c+d)
+
 # test some matrix operations don't throw errors
 X = [0 b c; d e f; g h i]
 @test iszero(simplify(det(X) - ((d * ((b * i) - (c * h))) + (g * ((b * f) - (c * e))))))
@@ -22,7 +25,7 @@ F = lu(X)
 R = simplify.(F.L * F.U - X[F.p, :], polynorm=true)
 @test iszero(R)
 @test simplify.(F \ X) == I
-@test Symbolics._solve(X, X) == I
+@test ModelingToolkit._solve(X, X, true) == I
 inv(X)
 qr(X)
 
@@ -53,24 +56,25 @@ D = sparse([1, 2], [2, 1], [d, d])
 
 @test isequal(C * D, sparse([1,2], [1,2], [c * d, c * d]))
 
-@variables t σ ρ β
+@parameters t σ ρ β
 @variables x(t) y(t) z(t)
-
+D = Differential(t)
 Dx = Differential(x)
 Dy = Differential(y)
 Dz = Differential(z)
 
-eqs = [σ*(y-x),
-       x*(ρ-z)-y,
-       x*y - β*z]
-J = Num[Dx(eqs[1]) Dy(eqs[1]) Dz(eqs[1])
-        Dx(eqs[2]) Dy(eqs[2]) Dz(eqs[2])
-        Dx(eqs[3]) Dy(eqs[3]) Dz(eqs[3])]
+eqs = [D(x) ~ σ*(y-x),
+       D(y) ~ x*(ρ-z)-y,
+       D(z) ~ x*y - β*z]
+J = Num[Dx(eqs[1].rhs) Dy(eqs[1].rhs) Dz(eqs[1].rhs)
+ Dx(eqs[2].rhs) Dy(eqs[2].rhs) Dz(eqs[2].rhs)
+ Dx(eqs[3].rhs) Dy(eqs[3].rhs) Dz(eqs[3].rhs)]
 
 J = expand_derivatives.(J)
 using LinearAlgebra
 luJ = lu(J,Val(false))
 
+using ModelingToolkit
 @variables M[1:2,1:2]
 inv(M)
 
@@ -85,3 +89,43 @@ M \ reshape(b,2,1)
 M = [1 a; 0 2]
 M \ b
 M \ [1, 2]
+
+# test det
+@variables X[1:4,1:4]
+d1 = det(X, laplace=true)
+d2 = det(X, laplace=false)
+_det1 = eval(build_function(d1, X))
+_det2 = eval(build_function(d2, X))
+A = [1 1 1 1
+     1 0 1 1
+     1 1 0 1
+     1 1 1 0]
+@test _det1(A) == -1
+@test _det2(A) == -1
+
+@variables X[1:3,1:3]
+d1 = det(X, laplace=true)
+d2 = det(X, laplace=false)
+_det1 = eval(build_function(d1, X))
+_det2 = eval(build_function(d2, X))
+A = [1 1 1
+     1 0 1
+     1 1 1]
+@test _det1(A) == 0
+@test _det2(A) == 0
+
+@variables a b c d
+z1 = a + b * im
+z2 = c + d * im
+@test z1 * 2 - Complex(2a, 2b) == 0
+@test isequal(2z1, Complex(2a, 2b))
+@test isequal(z1 / z1, 1)
+@test isequal(z1 / z2, Complex((a*c + b*d)/(c^2 + d^2), (b*c - a*d)/(c^2 + d^2)))
+@test isequal(1 / z2, Complex(c/(c^2 + d^2), -d/(c^2 + d^2)))
+@test isequal(z1 * z2, Complex(a*c - b*d, a*d + b*c))
+@test isequal(z1 - z2, Complex(a - c, b - d))
+@test isequal(z1 + z2, Complex(a + c, b + d))
+@test isequal(z1 + 2, Complex(a + 2, b))
+@test isequal(2 + z1, Complex(2 + a, b))
+@test isequal(z1 - 2, Complex(a - 2, b))
+@test isequal(2 - z1, Complex(2 - a, -b))
diff --git a/test/runtests.jl b/test/runtests.jl
index d114104b8..f312aafeb 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -1,4 +1,10 @@
 using SafeTestsets, Test
 
 @safetestset "Differentiation Test" begin include("diff.jl") end
-@safetestset "Array Test" begin include("array.jl") end
+@safetestset "Overloading Test" begin include("overloads.jl") end
+
+if haskey(ENV, "CI")
+    using Pkg
+    Pkg.add(url="https://github.com/SciML/ModelingToolkit.jl.git", rev="master")
+    Pkg.test("ModelingToolkit")
+end