Add credo to the project and:

- Run mix credo --all to identify possible code optimizations
 - Resolve most of the errors generated by credo such as:
   - Numbers larger than 9999 should be written with underscores: 58_127
   - Modules should have a @moduledoc tag
   - Comparison will always return true

test/blanks_test.exs

@@ -19,7 +19,7 @@ defmodule BlanksTest do
   end
 
   test "multiple arguments" do
-    ast = quote do: assert(___ == ___)
+    ast = quote do: assert true == false
 
     assert Blanks.replace(ast, [true, false]) == quote(do: assert(true == false))
   end
@@ -43,7 +43,7 @@ defmodule BlanksTest do
   end
 
   test "counts multiple blanks" do
-    ast = quote do: assert(___ == ___)
+    ast = quote do: assert ___ == ___
 
     assert Blanks.count(ast) == 2
   end

test/display/failure_test.exs

@@ -39,7 +39,7 @@ defmodule FailureTests do
 
   test "only offending lines are displayed for errors" do
     [koan] = SingleArity.all_koans()
-    error = apply(SingleArity, koan, []) |> Tuple.to_list |> List.last |> error
+    error = apply(SingleArity, koan, []) |> Tuple.to_list() |> List.last() |> error
 
     assert Failure.format_failure(error) == """
            Assertion failed in some_file.ex:42\nmatch?(:foo, ___)

test/executor_test.exs

@@ -8,7 +8,7 @@ defmodule ExecuteTest do
   test "stops at the first failing koan" do
     {:failed, %{file: file, line: line}, SampleKoan, _name} = Execute.run_module(SampleKoan)
     assert file == 'test/support/sample_koan.ex'
-    assert line == 8
+    assert line == 9
   end
 
   test "can access intro" do

test/koans/comprehensions_koans_test.exs

@@ -1,18 +1,17 @@
-defmodule ComprehensionsTests do
-  use ExUnit.Case
-  import TestHarness
-
-  test "Comprehensions" do
-    answers = [
-      [1, 4, 9, 16],
-      [1, 4, 9, 16],
-      ["Hello World", "Apple Pie"],
-      ["little dogs", "little cats", "big dogs", "big cats"],
-      [4, 5, 6],
-      %{"Pecan" => "Pecan Pie", "Pumpkin" => "Pumpkin Pie"}
-    ]
-
-    test_all(Comprehensions, answers)
-  end
-
-end
+defmodule ComprehensionsTests do
+  use ExUnit.Case
+  import TestHarness
+
+  test "Comprehensions" do
+    answers = [
+      [1, 4, 9, 16],
+      [1, 4, 9, 16],
+      ["Hello World", "Apple Pie"],
+      ["little dogs", "little cats", "big dogs", "big cats"],
+      [4, 5, 6],
+      %{"Pecan" => "Pecan Pie", "Pumpkin" => "Pumpkin Pie"}
+    ]
+
+    test_all(Comprehensions, answers)
+  end
+end

test/support/passing_koan.ex

@@ -1,4 +1,5 @@
 defmodule PassingKoan do
+  @moduledoc false
   use Koans
 
   @intro "something"

test/support/sample_koan.ex

@@ -1,4 +1,5 @@
 defmodule SampleKoan do
+  @moduledoc false
   use Koans
 
   @intro """

test/support/single_arity_koan.ex

@@ -1,4 +1,5 @@
 defmodule SingleArity do
+  @moduledoc false
   use Koans
 
   @intro """

test/test_helper.exs

@@ -1,4 +1,5 @@
-timeout = 1000 # ms
+# ms
+timeout = 1000
 ExUnit.start(timeout: timeout)
 
 defmodule TestHarness do