Add convergence tests for Ralston4

Author: YingboMa

test/ode_tableau_convergence_tests.jl

@@ -63,6 +63,11 @@ for i = 1:2 # 1 = num, 2 = ExplicitRK
   sim = test_convergence(dts,prob,tabalg)
   @test abs(sim.𝒪est[:l∞]-4) < testTol
 
+  @test sum(i -> sqrt(residual_order_condition(constructRalston4(), i, +)), 1:4) < eps(1.0)
+  tabalg = ExplicitRK(tableau=constructRalston4())
+  sim = test_convergence(dts,prob,tabalg)
+  @test abs(sim.𝒪est[:l∞]-4) < testTol
+
   tabalg = ExplicitRK(tableau=constructSSPRK104())
   sim = test_convergence(dts,prob,tabalg)
   @test abs(sim.𝒪est[:l∞]-4) < testTol