From ff443e48dbc9120f015116663aed92f2042f730a Mon Sep 17 00:00:00 2001
From: Herman Sletmoen <hermansletmoen@gmail.com>
Date: Thu, 18 Jul 2024 12:43:43 +0200
Subject: [PATCH] Test a system that really should have a guess

---
 test/initializationsystem.jl | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/test/initializationsystem.jl b/test/initializationsystem.jl
index f4097ecd97..13d797d189 100644
--- a/test/initializationsystem.jl
+++ b/test/initializationsystem.jl
@@ -456,3 +456,11 @@ sys = structural_simplify(unsimp; fully_determined = false)
 sys = extend(sysx, sysy)
 @test length(equations(generate_initializesystem(sys))) == 2
 @test length(ModelingToolkit.guesses(sys)) == 1
+
+# https://github.com/SciML/ModelingToolkit.jl/issues/2873
+@testset "Error on missing defaults" begin
+    @variables x(t) y(t)
+    @named sys = ODESystem([x^2 + y^2 ~ 25, D(x) ~ 1], t)
+    ssys = structural_simplify(sys)
+    @test_throws ArgumentError prob = ODEProblem(ssys, [x => 3], (0, 1), [] #=; guesses = [y => 5]=#)
+end