require "../../../src/engine/gravity/field"

describe Gravity::Field do
  earth = Gravity::Body(2).new(mass: 5972200000000000000000000.0, position: Vector[0.0, 0.0])
  earth_surface = Vector[6371000.0, 0.0]

  it "accelerate arbitrary points" do
    field = Gravity::Field(2).new([earth])
    field = Gravity::Field(2).new(earth)
    field = Gravity::Field(2).new({earth})
    earth.acceleration(earth_surface).magnitude.round(2).should eq(9.82)
  end

  it "allow zero gravity field" do
    g = Gravity::Field(2).zero
    g.acceleration(earth_surface).magnitude.round(2).should eq(0)
    g = Gravity::Field(2).new
    g.acceleration(earth_surface).magnitude.round(2).should eq(0)
  end
end