# Project Euler problem #25

```python
#python program with test cases to find the index of 1000 digits fibonacci number
import unittest
def fib_index(n):
	if type(n)!=int:
		return 'Type error'
	if n<1 :
		return None
	count=2
	length=1
	a,b=1,1
	while length!=n:
	    c=a+b
	    a=b
	    b=c
	    count+=1
	    length=len(str(b))
	return count
print(fib_index(1000))

class test_cases(unittest.TestCase):
    def test_fib_index(self):
        self.assertEqual(fib_index(-10),None)
        self.assertEqual(fib_index('456'), 'Type error')
        self.assertEqual(fib_index(3),12)
        
if __name__ == "__main__":
    unittest.main()
```