fix: fix jumpsystem test

Author: vyudu

src/systems/callbacks.jl

@@ -283,7 +283,7 @@ function make_affect(affect::Vector{Equation}; discrete_parameters = Any[],
     for eq in affect
         if !haspre(eq) && !(symbolic_type(eq.rhs) === NotSymbolic() ||
              symbolic_type(eq.lhs) === NotSymbolic())
-            @warn "Affect equation $eq has no `Pre` operator. As such it will be interpreted as an algebraic equation to be satisfied after the callback. If you intended to use the value of a variable x before the affect, use Pre(x)."
+            @warn "Affect equation $eq has no `Pre` operator. As such it will be interpreted as an algebraic equation to be satisfied after the callback. If you intended to use the value of a variable x before the affect, use Pre(x). Errors may be thrown if there is no `Pre` and algebraic equations are unsatisfiable, such as X ~ X + 1."
         end
         collect_vars!(dvs, params, eq, iv; op = Pre)
         diffvs = collect_applied_operators(eq, Differential)

test/jumpsystem.jl

@@ -556,7 +556,7 @@ end
     @parameters a b
     eq = D(X) ~ a
     rate = b * X
-    affect = [X ~ X - 1]
+    affect = [X ~ Pre(X) - 1]
     crj = ConstantRateJump(rate, affect)
     @named jsys = JumpSystem([crj, eq], t, [X], [a, b])
     jsys = complete(jsys)

test/symbolic_events.jl

@@ -638,8 +638,8 @@ end
     sol = solve(prob, Tsit5(), saveat = 0.1)
 
     @test typeof(oneosc_ce_simpl) == ODESystem
-    @test sol[1, 6] < 1.0 # test whether x(t) decreases over time
-    @test sol[1, 18] > 0.5 # test whether event happened
+    @test sol(0.5, idxs = oscce.x) < 1.0 # test whether x(t) decreases over time
+    @test sol(1.5, idxs = oscce.x) > 0.5 # test whether event happened
 end
 
 @testset "Additional SymbolicContinuousCallback options" begin