Decouple from ExUnit

README.md

@@ -141,6 +141,12 @@ def project do
 end
 ```
 
+## Integrating a testing library
+
+By default, `use WhiteBread.Context` will import ExUnit.Assertions. If you're not using ExUnit, you'll probably want to override this default by calling `use WhiteBread.Context, test_library: :some_other_library_name`.
+
+At the moment, the only library names available are `:ex_unit` (same as the default), `:espec`, and `nil` (which skips the test library setup step altogether).
+
 # Next steps - Additional Suites and subcontexts
 
 After following the getting started steps you may find your default context starts to get a bit large.

lib/white_bread/context.ex

@@ -4,12 +4,16 @@ defmodule WhiteBread.Context do
   alias WhiteBread.Context.Setup
 
   @step_keywords [:given_, :when_, :then_, :and_, :but_]
+  @default_test_library :ex_unit
 
   @doc false
-  defmacro __using__(_opts) do
+  defmacro __using__(opts \\ []) do
+    opts = Keyword.merge [test_library: @default_test_library], opts
+    [test_library: test_library] = opts
+
     quote do
       import WhiteBread.Context
-      import ExUnit.Assertions
+      unquote(import_test_library test_library)
 
       @behaviour WhiteBread.ContextBehaviour
 
@@ -110,5 +114,15 @@ defmodule WhiteBread.Context do
     end
   end
 
-
+  defp import_test_library(test_library) do
+    case test_library do
+      :ex_unit -> quote do: import ExUnit.Assertions
+      :espec -> quote do
+        require ESpec
+        use ESpec
+      end
+      nil -> quote do: true
+      _ -> raise ArgumentError, "#{inspect test_library} is not a recognized value for :test_library. Recognized values are :ex_unit, :espec, and nil."
+    end
+  end
 end