test: add state priority to tests for predictable state selection

Author: AayushSabharwal

lib/ModelingToolkitBase/test/odesystem.jl

@@ -777,7 +777,7 @@ if @isdefined(ModelingToolkit)
     ## double integrator
 
     function double_int(; name)
-        @variables u(t) x(t) v(t)
+        @variables u(t) x(t) [state_priority = 1] v(t) [state_priority = 1]
 
         eqs = [D(x) ~ v, D(v) ~ u]
         return System(eqs, t; name)

test/structural_transformation/tearing.jl

@@ -154,7 +154,7 @@ newsys = tearing(nlsys)
 ###
 using ModelingToolkit, OrdinaryDiffEq, BenchmarkTools
 @parameters p
-@variables x(t) y(t) z(t)
+@variables x(t) [state_priority = 1] y(t) z(t)
 eqs = [
     D(x) ~ z * h
     0 ~ x - y