factorial

factorial.ex

defmodule Factorial do
  def call(n) do
    case n do
      0 -> 1
      _ -> n * call(n-1)
    end
  end
end

factorial_test.ex

defmodule FactorialTest do
  use ExUnit.Case
  doctest Factorial

  test "factorial 0" do
    assert Factorial.call(0) == 1
  end

  test "factorial 5" do
    assert Factorial.call(5) == 120
  end

  test "factorial 3" do
    assert Factorial.call(3) == 6
  end
end

# ilya@ilya-UX303LN:~/Repository/factorial$ mix test
# ...
#
# Finished in 0.03 seconds
# 3 tests, 0 failures
#
# Randomized with seed 947461