test.describe("Powers of 10")
test.assert_equals(digits(0), 1)
n = 1
for i in range(1,21):
  n *= 10
  test.assert_equals(digits(n), i+1)
import sys
test.assert_equals(digits(sys.maxsize), 19)

test.describe("Powers of 10 minus 1")
n = 1
for i in range(1,21):
  n *= 10
  test.assert_equals(digits(n-1), i)
    
test.describe("Powers of 10 half")
n = 1
for i in range(1, 21):
  n *= 10
  test.assert_equals(digits(n // 2), i)
    
test.describe("Negative powers of 10")
n = 1
for i in range(1, 21):
  n *= 10
  test.assert_equals(digits(-n), i+1)