function test_convergence_p3_dg()
  @testset "---- P3 Conservative DG Convergence Tests -----" begin
    start_dir = pwd()

    cd("./m1")
    fname = "input_vals_vortex3.jl"
    mesh, sbp, eqn, opts = solvePDE(fname)
    fname = "input_vals_vortex4.jl"
    mesh, sbp, eqn, opts = solvePDE(fname)

    cd("../m2")
    fname = "input_vals_vortex3.jl"
    mesh, sbp, eqn, opts = solvePDE(fname)
    fname = "input_vals_vortex4.jl"
    mesh, sbp, eqn, opts = solvePDE(fname)

    cd("..")

    slope = calc_line()
    println("slope = ", slope)

    data = readdlm("err_data.dat")
    err_vals = data[:, 2]
    #println("err_vals = ", err_vals)

    slope_val = 3.84
    slope_margin = 0.1

    @test  slope  > slope_val - slope_margin
    @test  slope  < slope_val + slope_margin

    err_val = 6.87e-5
    slope_fac = 1.25
    println("err_vals[1] = ", err_vals[1])
    @test  err_vals[1]  > err_val/slope_fac
    @test  err_vals[1]  < err_val*slope_fac

  end

  return nothing
end
