Add a Bitfield test

test/petal/bitfield_test.exs

@@ -0,0 +1,18 @@
+defmodule Petal.BitfieldTest do
+  use ExUnit.Case
+
+  alias Petal.Bitfield
+
+  describe "new/1" do
+    test "returns a new bitfield of size `x`" do
+      bitfield = Bitfield.new(64)
+      assert bitfield.size == 64
+      assert bitfield.bitfield == <<0, 0, 0, 0, 0, 0, 0, 0>>
+    end
+  end
+
+  test "to_string/1" do
+    bitfield = Bitfield.new(8)
+    assert to_string(bitfield) =~ ~r/Field data: 00000000/
+  end
+end

test/petal/bytes_test.exs

@@ -1,5 +1,6 @@
 defmodule Petal.BytesTest do
   use ExUnit.Case
+  doctest Petal.Bytes
 
   alias Petal.Bytes