Added Elixir Recursion tests

test/elixir_recursion_test.exs

@@ -0,0 +1,56 @@
+defmodule RecursionTest do
+  use ExUnit.Case
+  import ExUnit.CaptureIO
+
+  defmodule Recursion do
+    def print_multiple_times(msg, n) when n > 0 do
+      IO.puts(msg)
+      print_multiple_times(msg, n - 1)
+    end
+
+    def print_multiple_times(_msg, 0) do
+      :ok
+    end
+  end
+
+  defmodule Math do
+    def sum_list([head | tail], accumulator) do
+      sum_list(tail, head + accumulator)
+    end
+
+    def sum_list([], accumulator) do
+      accumulator
+    end
+
+    def double_each([head | tail]) do
+      [head * 2 | double_each(tail)]
+    end
+
+    def double_each([]) do
+      []
+    end
+  end
+
+  test "Recursion.print_multiple_times/2 prints the message n times" do
+    assert capture_io(fn -> Recursion.print_multiple_times("Hello!", 3) end) ==
+             "Hello!\nHello!\nHello!\n"
+  end
+
+  test "Recursion.print_multiple_times/2 returns :ok when n is 0" do
+    assert Recursion.print_multiple_times("Hello!", 0) == :ok
+  end
+
+  test "Recursion.print_multiple_times/2 raises a FunctionClauseError when n is negative" do
+    assert_raise FunctionClauseError, fn -> Recursion.print_multiple_times("Hello!", -1) end
+  end
+
+  test "Math.sum_list/2 returns the sum of a list of numbers" do
+    assert Math.sum_list([1, 2, 3], 0) == 6
+    assert Math.sum_list([], 0) == 0
+  end
+
+  test "Math.double_each/1 doubles each element in the list" do
+    assert Math.double_each([1, 2, 3]) == [2, 4, 6]
+    assert Math.double_each([]) == []
+  end
+end