@testset "Propagator" begin

  println("Testing propagator")

  using Thesis: prop_one

  # Set up
  start_mass = 10_000.
  start = [oe_to_xyz([ (μs["Earth"]*(rand(3600*1.5:0.01:3600*4)/(2π))^2)^(1/3),
                        rand(0.01:0.01:0.5),
                        rand(0.01:0.01:0.45π),
                        0.,
                        0.,
                        1. ], μs["Earth"]); start_mass]
  stepsize = rand(100.0:0.01:500.0)

  # Test that Laguerre-Conway is the default propagator for spacecrafts
  craft = Sc("no_thrust")
  state = prop_one([0., 0., 0.], start, craft, μs["Earth"], stepsize)
  @test laguerre_conway(start, μs["Earth"], stepsize) ≈ state[1:6]
  @test state[7] == start_mass

  # Test that mass is reduced properly
  craft = Sc("test")
  state = prop_one([1., 0., 0.], start, craft, μs["Earth"], stepsize)
  @test state[7] == start_mass - craft.mass_flow_rate*stepsize
  
  # Test that a bad ΔV throws an error
  @test_throws ErrorException prop_one([1.5, 0., 0.], start, craft, μs["Earth"], stepsize)

end