1require "spec_helper"
 2
 3def factorial(n)
 4  if n == 0
 5    1
 6  else
 7    n * factorial(n-1)
 8  end
 9end
10
11def fibonacci(n)
12  n < 2 ? n : fibonacci(n - 1) + fibonacci(n - 2)
13end
14
15def fibonacci_enumerator
16  Enumerator.new do |yielder|
17    i, j = 0, 1
18    loop do
19      i, j = j, i + j
20      yielder.yield i
21    end
22  end
23end
24
25describe "fibonacci" do
26  let(:sut) { Fibonacci.new }
27
28  xit "should return the correct result" do
29    #0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144
30    expect(sut.get(0)).to eq(0)
31    expect(sut.get(1)).to eq(1)
32  end
33
34  it "should return the first n numbers in fibonacci" do
35    f = ->(x){ x < 2 ? x : f.call(x-1) + f.call(x-2) }
36    20.times do |n|
37      expect(fibonacci(n)).to eq(f.call(n))
38    end
39  end
40
41  it "can enumerate forever" do
42    fibonacci_enumerator.take_while { |n| n < 1000 }
43  end
44
45  it "can do factorial" do
46    (1..10).each do |n|
47      expect(factorial(n)).to eq((1..n).inject { |total, i| (i) * total })
48    end
49  end
50end