def test_loss_vs_dep_value():
iv = 100
y = 5
ia = 0
dv, loss = calculate(iv, years=y, initial_age=ia, rate=TWO_STAGE_RATE)
for i in range(y):
assert loss[i] == approx(TWO_STAGE_RATE(i) * dv[i])
def test_depreciated_value_result_sizes():
iv = 100 # initial value
y = 5 # num years
ia = 0 # initial age
dv, loss = calculate(iv, years=y, initial_age=ia, rate=FLAT_RATE_15)
assert len(dv) == y
assert len(loss) == y
def test_depreciated_value():
iv = 100
y = 5
ia = 0
dv, _ = calculate(iv, years=y, initial_age=ia, rate=FLAT_RATE_15)
r = 1 - FLAT_RATE_15(0)
assert dv[0] == approx(iv)
assert dv[1] == approx(dv[0] * r)
assert dv[2] == approx(dv[1] * r)
assert dv[3] == approx(dv[2] * r)
assert dv[4] == approx(dv[3] * r)
def test_depreciation_on_10K_over_5_years_at_11percent():
actual, _ = calculate(10000, years=5, initial_age=0, rate=FlatRate(0.11))
expected = [10000.000, 8900.000, 7921.000, 7049.690, 6274.224]
assert_allclose(actual, expected, atol=0.001)
def test_cumulative_loss():
iv = 15000
y = 10
ia = 0
dv, loss = calculate(iv, years=y, initial_age=ia, rate=TWO_STAGE_RATE)
assert dv[0] - dv[-1] == approx(loss[0:-1].sum())
def test_depreciated_value_second_year():
iv = 1000
y = 5
ia = 0 # initial age
dv, _ = calculate(iv, years=y, initial_age=ia, rate=FLAT_RATE_15)
assert dv[1] == approx(iv * (1 - FLAT_RATE_15(0)))
def test_depreciated_value_first_year():
iv = 100
y = 5
ia = 0 # initial age
dv, _ = calculate(iv, years=y, initial_age=ia, rate=FLAT_RATE_15)
assert dv[0] == approx(iv)