Update tests

Author: YingboMa

test/nonlinearsystem.jl

@@ -113,10 +113,10 @@ D = Differential(t)
 @named subsys = convert_system(ODESystem, lorenz1, t)
 @named sys = ODESystem([D(subsys.x) ~ subsys.x + subsys.x], t, systems = [subsys])
 sys = structural_simplify(sys)
-u0 = [subsys.x => 1, subsys.z => 2.0]
+u0 = [subsys.x => 1, subsys.z => 2.0, subsys.y => 1.0]
 prob = ODEProblem(sys, u0, (0, 1.0), [subsys.σ => 1, subsys.ρ => 2, subsys.β => 3])
-sol = solve(prob, Rodas5())
-@test sol[subsys.x] + sol[subsys.y] - sol[subsys.z] ≈ sol[subsys.u]
+sol = solve(prob, FBDF(), reltol = 1e-7, abstol = 1e-7)
+@test sol[subsys.x] + sol[subsys.y] - sol[subsys.z]≈sol[subsys.u] atol=1e-7
 @test_throws ArgumentError convert_system(ODESystem, sys, t)
 
 @parameters t σ ρ β