Test code for my ODE says it is wrong, while I have proof it's right

I am following this tutorial on a Lokta Volterra (Predator-prey) problem. I managed to product a plot that looks like theirs. However, I want a definitive proof that my implementation is correct.

My first idea is to calculate rabbits[t]-rabbits[t-1] and compare with the analytical equation of the number of rabbits to see if they are the same. However I cannot make the test code work.

The test code

def test(rabbits, foxes, ts, t):
    '''
    rabbits, foxes, ts: array of numbers of rabbits, foxes and time points
    t: a specific timestep (t < len(ts))
    '''
    calculated_drabbit_dt=(rabbits[t+1]-rabbits[t]) 
    analytic_drabbit_dt=a*rabbits[t]-b*rabbits[t]*foxes[t]  # equation is also in link above, rabbit is called u
    print([calculated_drabbit_dt], [analytic_drabbit_dt])
    assert np.isclose([calculated_drabbit_dt], [analytic_drabbit_dt])

test(rabbits_2, foxes_2, t, t=166)

Why did I do wrong in my test code?