def test_equal_probability():
""" Check particles have equal probability of movement. """
from numpy import array, sqrt, count_nonzero
energy = MagicMock()
density = array([1, 0, 99])
mc = MonteCarlo(energy, density)
changes_at_zero = [(density - mc.change_density(density))[0] != 0
for i in range(10000)]
assert count_nonzero(changes_at_zero) == approx(
0.01 * len(changes_at_zero), 0.5 * sqrt(len(changes_at_zero)))
def test_move_particle_one_over():
""" Check density is change by a particle hopping left or right. """
from numpy import nonzero, multiply
from numpy.random import randint
energy = MagicMock()
for i in range(100):
# Do this n times, to avoid
# issues with random numbers
# Create density
density = randint(50, size=randint(2, 6))
mc = MonteCarlo(energy, density)
# Change it
new_density = mc.change_density(density)
# Make sure any movement is by one
indices = nonzero(density - new_density)[0]
assert len(indices) == 2, "densities differ in two places"
assert (multiply.reduce(
(density -
new_density)[indices]) == -1), "densities differ by + and - 1"
