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

@@ -6,10 +6,13 @@ defmodule WhiteBread.Context do
   @step_keywords [:given_, :when_, :then_, :and_, :but_]
 
   @doc false
-  defmacro __using__(_opts) do
+  defmacro __using__(opts \\ []) do
+    opts = Keyword.merge [test_library: :ex_unit], 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 +113,15 @@ 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, ":test_library must be one of :ex_unit, :espec, or nil."
+    end
+  end
 end