diff --git a/lib/faker/datetime.ex b/lib/faker/datetime.ex
index 918b7eee1..35d0d1b10 100644
--- a/lib/faker/datetime.ex
+++ b/lib/faker/datetime.ex
@@ -14,7 +14,7 @@ defmodule Faker.DateTime do
       #=>  std_offset: 0, time_zone: "Etc/UTC", utc_offset: 0, year: 2016,
       #=>  zone_abbr: "UTC"}
   """
-  @spec backward(integer) :: DateTime.t
+  @spec backward(integer) :: DateTime.t()
   def backward(days) do
     forward(-days)
   end
@@ -30,7 +30,7 @@ defmodule Faker.DateTime do
       #=>  std_offset: 0, time_zone: "Etc/UTC", utc_offset: 0, year: 2016,
       #=>  zone_abbr: "UTC"}
   """
-  @spec forward(integer) :: DateTime.t
+  @spec forward(integer) :: DateTime.t()
   def forward(days) do
     sign = if days < 0, do: -1, else: 1
 
@@ -53,33 +53,56 @@ defmodule Faker.DateTime do
       #=>  std_offset: 0, time_zone: "Etc/UTC", utc_offset: 0, year: 2016,
       #=>  zone_abbr: "UTC"}
   """
-  @spec between(Date.t | NaiveDateTime.t | DateTime.t, Date.t | NaiveDateTime.t | DateTime.t) :: DateTime.t
+  @spec between(
+          Date.t() | NaiveDateTime.t() | DateTime.t(),
+          Date.t() | NaiveDateTime.t() | DateTime.t()
+        ) :: DateTime.t()
   def between(%Date{} = from, %Date{} = to) do
     between(date_to_datetime(from), date_to_datetime(to))
   end
+
   def between(%NaiveDateTime{} = from, %NaiveDateTime{} = to) do
     between(naivedatetime_to_datetime(from), naivedatetime_to_datetime(to))
   end
+
   def between(from, to) do
     unix_between(to_timestamp(from), to_timestamp(to))
   end
 
   # private
 
-  @spec date_to_datetime(Date.t) :: DateTime.t
+  @spec date_to_datetime(Date.t()) :: DateTime.t()
   defp date_to_datetime(date) do
-    %DateTime{calendar: Calendar.ISO, day: date.day, hour: 0, minute: 0,
-              month: date.month, second: 0, time_zone: "Etc/UTC",
-              utc_offset: 0, std_offset: 0, year: date.year, zone_abbr: "UTC"}
+    %DateTime{
+      calendar: Calendar.ISO,
+      day: date.day,
+      hour: 0,
+      minute: 0,
+      month: date.month,
+      second: 0,
+      time_zone: "Etc/UTC",
+      utc_offset: 0,
+      std_offset: 0,
+      year: date.year,
+      zone_abbr: "UTC"
+    }
   end
 
-  @spec naivedatetime_to_datetime(NaiveDateTime.t) :: DateTime.t
+  @spec naivedatetime_to_datetime(NaiveDateTime.t()) :: DateTime.t()
   defp naivedatetime_to_datetime(naivedatetime) do
-    %DateTime{calendar: naivedatetime.calendar, day: naivedatetime.day,
-              hour: naivedatetime.hour, minute: naivedatetime.minute,
-              month: naivedatetime.month, second: naivedatetime.second,
-              time_zone: "Etc/UTC", utc_offset: 0, std_offset: 0,
-              year: naivedatetime.year, zone_abbr: "UTC"}
+    %DateTime{
+      calendar: naivedatetime.calendar,
+      day: naivedatetime.day,
+      hour: naivedatetime.hour,
+      minute: naivedatetime.minute,
+      month: naivedatetime.month,
+      second: naivedatetime.second,
+      time_zone: "Etc/UTC",
+      utc_offset: 0,
+      std_offset: 0,
+      year: naivedatetime.year,
+      zone_abbr: "UTC"
+    }
   end
 
   defp to_timestamp(datetime) do
diff --git a/lib/faker/file.ex b/lib/faker/file.ex
index 17c3c7f23..b717031eb 100644
--- a/lib/faker/file.ex
+++ b/lib/faker/file.ex
@@ -14,14 +14,20 @@ defmodule Faker.File do
   }
 
   @mimes %{
-    application: ~w(application/atom+xml application/ecmascript application/EDI-X12 application/EDIFACT application/json application/javascript application/ogg application/pdf application/postscript application/rdf+xml application/rss+xml application/soap+xml application/font-woff application/xhtml+xml application/xml-dtd application/xop+xml application/zip application/gzip),
-    audio: ~w(audio/basic audio/L24 audio/mp4 audio/mpeg audio/ogg audio/vorbis audio/vnd.rn-realaudio audio/vnd.wave audio/webm),
-    image: ~w(image/gif image/jpeg image/pjpeg image/png image/svg+xml image/tiff image/vnd.microsoft.icon),
+    application:
+      ~w(application/atom+xml application/ecmascript application/EDI-X12 application/EDIFACT application/json application/javascript application/ogg application/pdf application/postscript application/rdf+xml application/rss+xml application/soap+xml application/font-woff application/xhtml+xml application/xml-dtd application/xop+xml application/zip application/gzip),
+    audio:
+      ~w(audio/basic audio/L24 audio/mp4 audio/mpeg audio/ogg audio/vorbis audio/vnd.rn-realaudio audio/vnd.wave audio/webm),
+    image:
+      ~w(image/gif image/jpeg image/pjpeg image/png image/svg+xml image/tiff image/vnd.microsoft.icon),
     message: ~w(message/http message/imdn+xml message/partial message/rfc822),
-    model: ~w(model/example model/iges model/mesh model/vrml model/x3d+binary model/x3d+vrml model/x3d+xml),
-    multipart: ~w(multipart/mixed multipart/alternative multipart/related multipart/form-data multipart/signed multipart/encrypted),
+    model:
+      ~w(model/example model/iges model/mesh model/vrml model/x3d+binary model/x3d+vrml model/x3d+xml),
+    multipart:
+      ~w(multipart/mixed multipart/alternative multipart/related multipart/form-data multipart/signed multipart/encrypted),
     text: ~w(text/cmd text/css text/csv text/html text/javascript text/plain text/vcard text/xml),
-    video: ~w(video/mpeg video/mp4 video/ogg video/quicktime video/webm video/x-matroska video/x-ms-wmv video/x-flv)
+    video:
+      ~w(video/mpeg video/mp4 video/ogg video/quicktime video/webm video/x-matroska video/x-ms-wmv video/x-flv)
   }
 
   @categories_extensions Map.keys(@extensions)
@@ -33,9 +39,15 @@ defmodule Faker.File do
   ## Examples
 
       iex> Faker.File.file_extension()
-      #=> "mp3"
+      "wav"
+      iex> Faker.File.file_extension()
+      "wav"
+      iex> Faker.File.file_extension()
+      "doc"
+      iex> Faker.File.file_extension()
+      "mov"
   """
-  @spec file_extension() :: String.t
+  @spec file_extension() :: String.t()
   def file_extension do
     @categories_extensions
     |> pick
@@ -49,9 +61,15 @@ defmodule Faker.File do
   ## Examples
 
       iex> Faker.File.file_extension(:video)
-      #=> "webm"
+      "mov"
+      iex> Faker.File.file_extension(:image)
+      "tiff"
+      iex> Faker.File.file_extension(:audio)
+      "flac"
+      iex> Faker.File.file_extension(:office)
+      "xls"
   """
-  @spec file_extension(:atom) :: String.t
+  @spec file_extension(:atom) :: String.t()
   def file_extension(category) do
     category
     |> get_extensions_from_category()
@@ -64,11 +82,17 @@ defmodule Faker.File do
   ## Examples
 
       iex> Faker.File.file_name()
-      #=> "voluptaes.jpg"
+      "aliquam.jpg"
+      iex> Faker.File.file_name()
+      "deleniti.doc"
+      iex> Faker.File.file_name()
+      "qui.jpg"
+      iex> Faker.File.file_name()
+      "quibusdam.csv"
   """
-  @spec file_name() :: String.t
+  @spec file_name() :: String.t()
   def file_name do
-    Lorem.word <> "." <> file_extension()
+    Lorem.word() <> "." <> file_extension()
   end
 
   @doc """
@@ -78,11 +102,17 @@ defmodule Faker.File do
   ## Examples
 
       iex> Faker.File.file_name(:text)
-      #=> "reo.json"
+      "aliquam.txt"
+      iex> Faker.File.file_name(:video)
+      "sint.mp4"
+      iex> Faker.File.file_name(:image)
+      "consequatur.bmp"
+      iex> Faker.File.file_name(:audio)
+      "qui.wav"
   """
-  @spec file_name(:atom) :: String.t
+  @spec file_name(:atom) :: String.t()
   def file_name(category) do
-    Lorem.word <> "." <> file_extension(category)
+    Lorem.word() <> "." <> file_extension(category)
   end
 
   @doc """
@@ -91,9 +121,15 @@ defmodule Faker.File do
   ## Examples
 
       iex> Faker.File.mime_type()
-      #=> "application/atom+xml"
+      "text/css"
+      iex> Faker.File.mime_type()
+      "message/http"
+      iex> Faker.File.mime_type()
+      "application/ogg"
+      iex> Faker.File.mime_type()
+      "model/x3d+xml"
   """
-  @spec mime_type :: String.t
+  @spec mime_type :: String.t()
   def mime_type do
     @categories_mimes
     |> pick
@@ -108,9 +144,15 @@ defmodule Faker.File do
   ## Examples
 
       iex> Faker.File.mime_type(:image)
-      #=> "image/gif"
+      "image/vnd.microsoft.icon"
+      iex> Faker.File.mime_type(:audio)
+      "audio/mp4"
+      iex> Faker.File.mime_type(:application)
+      "application/xop+xml"
+      iex> Faker.File.mime_type(:video)
+      "video/mpeg"
   """
-  @spec mime_type(:atom) :: String.t
+  @spec mime_type(:atom) :: String.t()
   def mime_type(category) do
     category
     |> get_mimes_from_category()
diff --git a/test/faker/file_test.exs b/test/faker/file_test.exs
index a5e0a5104..41f4d0cd3 100644
--- a/test/faker/file_test.exs
+++ b/test/faker/file_test.exs
@@ -1,30 +1,5 @@
-defmodule FileTest do
+defmodule Faker.FileTest do
   use ExUnit.Case, async: true
 
-  test "file_extension/0" do
-    assert is_binary(Faker.File.file_extension)
-  end
-
-  test "file_extension/1" do
-    assert is_binary(Faker.File.file_extension(:audio))
-  end
-
-  test "mime_type/0" do
-    assert is_binary(Faker.File.mime_type)
-  end
-
-  test "mime_type/1" do
-    assert is_binary(Faker.File.mime_type(:video))
-  end
-
-  test "file_name/0" do
-    assert is_binary(Faker.File.file_name)
-    assert String.contains?(Faker.File.file_name, ".")
-  end
-
-  test "file_name/1" do
-    assert is_binary(Faker.File.file_name(:office))
-    assert String.contains?(Faker.File.file_name(:office), ".")
-  end
-
+  doctest Faker.File
 end
diff --git a/test/faker/gov/us_test.exs b/test/faker/gov/us_test.exs
index 221f070ac..ede683606 100644
--- a/test/faker/gov/us_test.exs
+++ b/test/faker/gov/us_test.exs
@@ -1,4 +1,4 @@
-defmodule Gov.UsTest do
+defmodule Faker.Gov.UsTest do
   use ExUnit.Case, async: true
 
   import Faker.Gov.Us