diff --git a/test/Blocks/nonlinear.jl b/test/Blocks/nonlinear.jl
index 3b5f58787..8fa2c2ade 100644
--- a/test/Blocks/nonlinear.jl
+++ b/test/Blocks/nonlinear.jl
@@ -20,7 +20,7 @@ using OrdinaryDiffEq: ReturnCode.Success
         prob = ODEProblem(sys, [int.x => 1.0], (0.0, 1.0))
 
         sol = solve(prob, Rodas4())
-        @test sol.retcode == Success
+        @test SciMLBase.successful_retcode(sol)
         @test sol[int.output.u][end] ≈ 2
         @test sol[sat.output.u][end] ≈ 0.8
     end
@@ -42,7 +42,7 @@ using OrdinaryDiffEq: ReturnCode.Success
         prob = ODEProblem(sys, unknowns(sys) .=> 0.0, (0.0, 10.0))
 
         sol = solve(prob, Rodas4())
-        @test sol.retcode == Success
+        @test SciMLBase.successful_retcode(sol)
         @test all(abs.(sol[lim.output.u]) .<= 0.5)
         @test all(isapprox.(sol[lim.output.u], _clamp.(sol[source.output.u], y_min, y_max),
             atol = 1e-2))
@@ -69,7 +69,7 @@ end
         prob = ODEProblem(sys, [int.x => 1.0], (0.0, 1.0))
         sol = solve(prob, Rodas4())
 
-        @test sol.retcode == Success
+        @test SciMLBase.successful_retcode(sol)
         @test all(sol[int.output.u][end] .≈ 2)
     end
 
@@ -89,7 +89,7 @@ end
         prob = ODEProblem(sys, [int.x => 1.0], (0.0, 10.0))
         sol = solve(prob, Rodas4())
 
-        @test sol.retcode == Success
+        @test SciMLBase.successful_retcode(sol)
         @test all(sol[dz.output.u] .<= 2)
         @test all(sol[dz.output.u] .>= -1)
         @test all(isapprox.(sol[dz.output.u],
@@ -115,7 +115,7 @@ end
 
     tS = 0.01
     sol = solve(prob, Rodas4(), saveat = tS, abstol = 1e-10, reltol = 1e-10)
-    @test sol.retcode == Success
+    @test SciMLBase.successful_retcode(sol)
     @test all(abs.(sol[rl.output.u]) .<= 0.51)
     @test all(-1 - 1e-5 .<= diff(sol[rl.output.u]) ./ tS .<= 1 + 1e-5) # just an approximation
 end
diff --git a/test/Electrical/analog.jl b/test/Electrical/analog.jl
index fbbeb24a9..1ac86ef73 100644
--- a/test/Electrical/analog.jl
+++ b/test/Electrical/analog.jl
@@ -48,7 +48,7 @@ using OrdinaryDiffEq: ReturnCode.Success
     # Plots.plot(sol; vars=[capacitor.v, voltage_sensor.v])
     # Plots.plot(sol; vars=[power_sensor.power, capacitor.i * capacitor.v])
     # Plots.plot(sol; vars=[resistor.i, current_sensor.i])
-    @test sol.retcode == Success
+    @test SciMLBase.successful_retcode(sol)
     @test sol[capacitor.v]≈sol[voltage_sensor.v] atol=1e-3
     @test sol[power_sensor.power]≈sol[capacitor.i * capacitor.v] atol=1e-3
     @test sol[resistor.i]≈sol[current_sensor.i] atol=1e-3
@@ -75,7 +75,7 @@ end
     sys = structural_simplify(model)
     prob = ODEProblem(sys, Pair[R2.i => 0.0], (0, 2.0))
     sol = solve(prob, Rodas4()) # has no state; does not work with Tsit5
-    @test sol.retcode == Success
+    @test SciMLBase.successful_retcode(sol)
     @test sol[short.v] == sol[R0.v] == zeros(length(sol.t))
     @test sol[R0.i] == zeros(length(sol.t))
     @test sol[R1.p.v][end]≈10 atol=1e-3
@@ -103,7 +103,7 @@ end
     sol = solve(prob, Tsit5())
 
     # Plots.plot(sol; vars=[source.v, capacitor.v])
-    @test sol.retcode == Success
+    @test SciMLBase.successful_retcode(sol)
     @test sol[capacitor.v][end]≈10 atol=1e-3
 end
 
@@ -127,7 +127,7 @@ end
     sol = solve(prob, Tsit5())
 
     # Plots.plot(sol; vars=[inductor.i, inductor.i])
-    @test sol.retcode == Success
+    @test SciMLBase.successful_retcode(sol)
     @test sol[inductor.i][end]≈10 atol=1e-3
 end
 
@@ -160,9 +160,9 @@ end
         sys = structural_simplify(model)
         prob = ODEProblem(sys, Pair[], (0.0, 10.0))
         sol = solve(prob, Tsit5())
-        @test sol.retcode == Success
+        @test SciMLBase.successful_retcode(sol)
         sol = solve(prob, Rodas4())
-        @test sol.retcode == Success
+        @test SciMLBase.successful_retcode(sol)
 
         # Plots.plot(sol; vars=[voltage.v, capacitor.v])
     end
@@ -188,7 +188,7 @@ end
     prob = ODEProblem(sys, Pair[], (0.0, 10.0))
     sol = solve(prob, Tsit5())
     y(x, st) = (x .> st) .* abs.(collect(x) .- st)
-    @test sol.retcode == Success
+    @test SciMLBase.successful_retcode(sol)
     @test sum(reduce(vcat, sol[capacitor.v]) .- y(sol.t, start_time))≈0 atol=1e-2
 end
 
@@ -228,7 +228,7 @@ end
           R1.v => 0.0]
     prob = ODEProblem(sys, u0, (0, 100.0))
     sol = solve(prob, Rodas4())
-    @test sol.retcode == Success
+    @test SciMLBase.successful_retcode(sol)
     @test sol[opamp.v2] == sol[C1.v] # Not a great one however. Rely on the plot
     @test sol[opamp.p2.v] == sol[sensor.v]
 
@@ -298,7 +298,7 @@ _damped_sine_wave(x, f, A, st, ϕ, d) = exp((st - x) * d) * A * sin(2 * π * f *
         prob = ODEProblem(vsys, u0, (0, 10.0))
         sol = solve(prob, dt = 0.1, Tsit5())
 
-        @test sol.retcode == Success
+        @test SciMLBase.successful_retcode(sol)
         @test sol[voltage.V.u]≈waveforms(i, sol.t) atol=1e-1
         @test sol[voltage.p.v] ≈ sol[voltage.V.u]
         # For visual inspection
@@ -364,7 +364,7 @@ end
         prob = ODEProblem(isys, u0, (0, 10.0))
         sol = solve(prob, dt = 0.1, Tsit5())
 
-        @test sol.retcode == Success
+        @test SciMLBase.successful_retcode(sol)
         @test sol[current.I.u]≈waveforms(i, sol.t) atol=1e-1
         @test sol[current.I.u]≈sol[current.p.i] atol=1e-1
         # For visual inspection
diff --git a/test/Magnetic/magnetic.jl b/test/Magnetic/magnetic.jl
index c81439fc1..0564aafa9 100644
--- a/test/Magnetic/magnetic.jl
+++ b/test/Magnetic/magnetic.jl
@@ -54,7 +54,7 @@ using OrdinaryDiffEq: ReturnCode.Success
     # Plots.plot(sol; vars=[r.i])
     # Plots.plot(sol; vars=[r_mFe.V_m, r_mFe.Phi])
 
-    @test sol.retcode == Success
+    @test SciMLBase.successful_retcode(sol)
     @test sol[r_mFe.Phi] == sol[r_mAirPar.Phi]
     @test all(sol[coil.port_p.Phi] + sol[r_mLeak.Phi] + sol[r_mAirPar.Phi] .== 0)
 end
diff --git a/test/Thermal/demo.jl b/test/Thermal/demo.jl
index 5403681fc..14b61b215 100644
--- a/test/Thermal/demo.jl
+++ b/test/Thermal/demo.jl
@@ -22,5 +22,5 @@ using OrdinaryDiffEq: ReturnCode.Success
     sys = structural_simplify(model)
     prob = ODEProblem(sys, [mass1.der_T => 1.0, mass2.der_T => 1.0], (0, 3.0))
     sol = solve(prob, Tsit5())
-    @test sol.retcode == Success
+    @test SciMLBase.successful_retcode(sol)
 end
diff --git a/test/Thermal/motor.jl b/test/Thermal/motor.jl
index c02d43538..a8f951256 100644
--- a/test/Thermal/motor.jl
+++ b/test/Thermal/motor.jl
@@ -46,7 +46,7 @@ using ModelingToolkitStandardLibrary.Blocks
     sol = solve(prob)
 
     # plot(sol; vars=[T_winding.T, T_core.T])
-    @test sol.retcode == Success
+    @test SciMLBase.successful_retcode(sol)
     @test sol[motor.T_winding.T] == sol[motor.winding.T]
     @test sol[motor.T_core.T] == sol[motor.core.T]
     @test sol[-motor.core.port.Q_flow] ≈
diff --git a/test/Thermal/piston.jl b/test/Thermal/piston.jl
index d514c5f4f..f1c8e3cb3 100644
--- a/test/Thermal/piston.jl
+++ b/test/Thermal/piston.jl
@@ -40,7 +40,7 @@ using ModelingToolkitStandardLibrary.Blocks
 
     # Heat-flow-rate is equal in magnitude
     # and opposite in direction
-    @test sol.retcode == Success
+    @test SciMLBase.successful_retcode(sol)
     # The initial value doesn't add up to absolute zero, while the rest do. To avoid
     # tolerance on the latter, the test is split in two parts.
     @test sol[piston.gas.Q_flow][1] + sol[piston.coolant.Q_flow][1]≈0 atol=1e-6
diff --git a/test/Thermal/thermal.jl b/test/Thermal/thermal.jl
index 85348faf5..a62ca5e61 100644
--- a/test/Thermal/thermal.jl
+++ b/test/Thermal/thermal.jl
@@ -29,7 +29,7 @@ using OrdinaryDiffEq: ReturnCode.Success
 
     # Check if Relative temperature sensor reads the temperature of heat capacitor
     # when connected to a thermal conductor and a fixed temperature source
-    @test sol.retcode == Success
+    @test SciMLBase.successful_retcode(sol)
     @test sol[reltem_sensor.T] + sol[tem_src.port.T] == sol[mass1.T] + sol[th_conductor.dT]
 
     @info "Building a two-body system..."
@@ -49,7 +49,7 @@ using OrdinaryDiffEq: ReturnCode.Success
     prob = ODEProblem(sys, u0, (0, 3.0))
     sol = solve(prob, Tsit5())
 
-    @test sol.retcode == Success
+    @test SciMLBase.successful_retcode(sol)
     m1, m2 = sol.u[end]
     @test m1≈m2 atol=1e-1
     mass_T = reduce(hcat, sol.u)
@@ -85,7 +85,7 @@ end
     prob = ODEProblem(sys, u0, (0, 3.0))
     sol = solve(prob, Tsit5())
 
-    @test sol.retcode == Success
+    @test SciMLBase.successful_retcode(sol)
     @test sol[th_conductor.dT] .* G == sol[th_conductor.Q_flow]
     @test sol[th_conductor.Q_flow] ≈ sol[hf_sensor1.Q_flow] + sol[flow_src.port.Q_flow]
 
@@ -127,7 +127,7 @@ end
     prob = ODEProblem(sys, u0, (0, 3.0))
     sol = solve(prob, Rodas4())
 
-    @test sol.retcode == Success
+    @test SciMLBase.successful_retcode(sol)
     @test sol[dissipator.dT] == sol[radiator.port_a.T] - sol[radiator.port_b.T]
     rad_Q_flow = G * σ * (T_gas^4 - T_coolant^4)
     @test sol[radiator.Q_flow] == fill(rad_Q_flow, length(sol[radiator.Q_flow]))
@@ -158,7 +158,7 @@ end
     prob = ODEProblem(sys, u0, (0, 3.0))
     sol = solve(prob, Rodas4())
 
-    @test sol.retcode == Success
+    @test SciMLBase.successful_retcode(sol)
     @test sol[collector.port_b.Q_flow] + sol[collector.port_a1.Q_flow] +
           sol[collector.port_a2.Q_flow] ==
           zeros(length(sol[collector.port_b.Q_flow]))