Revert "test: update some tests to account for use_symbolic = true"

This reverts commit cff3906.

Author: AayushSabharwal

test/components.jl

@@ -42,7 +42,7 @@ end
 completed_rc_model = complete(rc_model)
 @test isequal(completed_rc_model.resistor.n.i, resistor.n.i)
 @test ModelingToolkit.n_expanded_connection_equations(capacitor) == 2
-@test length(equations(structural_simplify(rc_model, allow_parameter = false))) == 1
+@test length(equations(structural_simplify(rc_model, allow_parameter = false))) == 2
 sys = structural_simplify(rc_model)
 @test_throws ModelingToolkit.RepeatedStructuralSimplificationError structural_simplify(sys)
 @test length(equations(sys)) == 1

test/implicit_discrete_system.jl

@@ -7,7 +7,7 @@ rng = StableRNG(22525)
 
 @testset "Correct ImplicitDiscreteFunction" begin
     @variables x(t) = 1
-    @mtkbuild sys = ImplicitDiscreteSystem([x(k) ~ abs(x(k)) * x(k - 1) - 3], t)
+    @mtkbuild sys = ImplicitDiscreteSystem([x(k) ~ x(k) * x(k - 1) - 3], t)
     tspan = (0, 10)
 
     # u[2] - u_next[1]

test/structural_transformation/index_reduction.jl

@@ -134,8 +134,8 @@ let pss_pendulum = partial_state_selection(pendulum)
 end
 
 let sys = structural_simplify(pendulum2)
-    @test length(equations(sys)) == 4
-    @test length(unknowns(sys)) == 4
+    @test length(equations(sys)) == 5
+    @test length(unknowns(sys)) == 5
 
     u0 = [
         x => sqrt(2) / 2,

test/structural_transformation/utils.jl

@@ -224,20 +224,20 @@ end
             xtt = default_toterm(unwrap(D(D(x))))
             @test mapping[x] == (0 ~ 1 - x^2 - y^2)
             @test mapping[y] == (D(y) ~ yt)
-            @test mapping[D(y)] == (D(yt) ~ (2xtt * x + 2xt^2 + 2yt^2) / (-2y))
-            @test mapping[D(x)] == (xt ~ -yt * y / x)
-            @test mapping[D(D(x))] == (0 ~ -xtt + x * λ)
-            @test length(mapping) == 6
+            @test mapping[D(y)] == (D(yt) ~ -g + y * λ)
+            @test mapping[D(x)] == (0 ~ -2xt * x - 2yt * y)
+            @test mapping[D(D(x))] == (xtt ~ x * λ)
+            @test length(mapping) == 5
 
             @testset "`rename_dummy_derivatives = false`" begin
                 mapping = map_variables_to_equations(sys; rename_dummy_derivatives = false)
 
                 @test mapping[x] == (0 ~ 1 - x^2 - y^2)
                 @test mapping[y] == (D(y) ~ yt)
-                @test mapping[yt] == (D(yt) ~ (2xtt * x + 2xt^2 + 2yt^2) / (-2y))
-                @test mapping[xt] == (xt ~ -yt * y / x)
-                @test mapping[xtt] == (0 ~ -xtt + x * λ)
-                @test length(mapping) == 6
+                @test mapping[yt] == (D(yt) ~ -g + y * λ)
+                @test mapping[xt] == (0 ~ -2xt * x - 2yt * y)
+                @test mapping[xtt] == (xtt ~ x * λ)
+                @test length(mapping) == 5
             end
         end
         @testset "DDEs" begin