added support for negative numbers

fib.py

@@ -6,6 +6,11 @@
 Negative numbers should return None
 """
 def fibonacci(position):
+  #this supports negative numbers
+  if position < 0: 
+    return None
+  if position == 0:
+    return 0
   if(position == 1 or position == 2):
     return 1
   return fibonacci(position - 1) + fibonacci(position - 2)
@@ -21,6 +26,30 @@ def fibonacci(position):
 assert(fibonacci(-1) == None)
 print("The -1st Fibonacci number: ", fibonacci(-1)) # should return None
 
+assert(fibonacci(1) == 1)
+print("The 1st Fibonacci number: ", fibonacci(1)) # should return 1
+
+assert(fibonacci(2) == 1)
+print("The 2nd Fibonacci number: ", fibonacci(2)) # should return 1
+
+assert(fibonacci(3) == 2)
+print("The 3rd Fibonacci number: ", fibonacci(3)) # should return 2
+
+assert(fibonacci(4) == 3)
+print("The 4th Fibonacci number: ", fibonacci(4)) # should return 3
+
+assert(fibonacci(5) == 5)
+print("The 5th Fibonacci number: ", fibonacci(5)) # should return 5
+
+assert(fibonacci(6) == 8)
+print("The 6th Fibonacci number: ", fibonacci(6)) # should return 8
+
+assert(fibonacci(7) == 13)
+print("The 7th Fibonacci number: ", fibonacci(7)) # should return 13
+
+assert(fibonacci(8) == 21)
+print("The 8th Fibonacci number: ", fibonacci(8)) # should return 21
+
 print("Code ran successfully!")