public void Envelope_Empty()
{
IEnvelope env = ObjectFactory.CreateEnvelope(0.0, 0.0, 0.0, 0.0);
Assert.True(env.IsEmpty());
env = null;
Assert.True(env.IsEmpty());
env = ObjectFactory.CreateEnvelope(-0.00000000001, -0.0000000000000001, 0.0000000000000000001, 0.000000000000001);
Assert.False(env.IsEmpty());
}