test: fix test for observed initialization

AayushSabharwal · AayushSabharwal · commit 8bfb15745f28 · 2024-09-09T13:12:07.000+05:30
diff --git a/test/initializationsystem.jl b/test/initializationsystem.jl
@@ -552,4 +552,4 @@ oprob_2nd_order_2 = ODEProblem(sys_2nd_order, u0_2nd_order_2, tspan, ps)
       SciMLBase.ReturnCode.InitialFailure
 sol = solve(oprob_2nd_order_2, Rosenbrock23()) # retcode: Success
 @test sol[Y][1] == 2.0
-@test sol[1, 2] == 0.5
+@test sol[D(Y)][1] == 0.5
