Add Plug.Test.init_test_session/2 for initializing a session (#469)

Author: Jérôme Guyon

lib/plug/session.ex

@@ -55,7 +55,10 @@ defmodule Plug.Session do
   end
 
   def call(conn, config) do
-    Conn.put_private(conn, :plug_session_fetch, fetch_session(config))
+    conn
+    |> Conn.put_private(:plug_session_init, conn.private[:plug_session] || %{})
+    |> Conn.put_private(:plug_session, nil)
+    |> Conn.put_private(:plug_session_fetch, fetch_session(config))
   end
 
   defp convert_store(store) do
@@ -76,6 +79,8 @@ defmodule Plug.Session do
           {nil, %{}}
         end
 
+      session = Map.merge(session, conn.private.plug_session_init)
+
       conn
       |> Conn.put_private(:plug_session, session)
       |> Conn.put_private(:plug_session_fetch, :done)

lib/plug/test.ex

@@ -123,4 +123,26 @@ defmodule Plug.Test do
       {key, value}, acc -> put_req_cookie(acc, to_string(key), value)
     end
   end
+
+  @doc """
+  Initializes the session with the given contents.
+
+  If the session has already been initialized, the new contents will be merged
+  with the previous ones.
+  """
+  @spec init_test_session(Conn.t, %{(String.t | atom) => any}) :: Conn.t
+  def init_test_session(conn, session) do
+    conn =
+      if conn.private[:plug_session_fetch] do
+        Conn.fetch_session(conn)
+      else
+        conn
+        |> Conn.put_private(:plug_session, %{})
+        |> Conn.put_private(:plug_session_fetch, :done)
+      end
+
+    Enum.reduce(session, conn, fn {key, value}, conn ->
+      Conn.put_session(conn, key, value)
+    end)
+  end
 end

test/plug/session_test.exs

@@ -127,4 +127,51 @@ defmodule Plug.SessionTest do
     opts = Plug.Session.init(store: :ets, key: "foobar", table: :some_table)
     assert opts.store == Plug.Session.ETS
   end
+
+  test "init_test_session/2" do
+    conn = conn(:get, "/") |> init_test_session(foo: "bar")
+    assert get_session(conn, :foo) == "bar"
+
+    conn = fetch_session(conn)
+    assert get_session(conn, :foo) == "bar"
+
+    conn = put_session(conn, :bar, "foo")
+    assert get_session(conn, :bar) == "foo"
+
+    conn = delete_session(conn, :bar)
+    refute get_session(conn, :bar)
+
+    conn = clear_session(conn)
+    refute get_session(conn, :foo)
+  end
+
+  test "init_test_session/2 merges values when called after Plug.Session" do
+    conn = conn(:get, "/") |> fetch_cookies
+
+    opts = Plug.Session.init(store: ProcessStore, key: "foobar")
+    conn = Plug.Session.call(conn, opts) |> fetch_session
+    conn = conn |> put_session(:foo, "bar") |> put_session(:bar, "foo")
+    conn = init_test_session(conn, bar: "bar", other: "other")
+
+    assert get_session(conn, :foo) == "bar"
+    assert get_session(conn, :other) == "other"
+    assert get_session(conn, :bar) == "bar"
+  end
+
+  test "init_test_session/2 merges values when called before Plug.Session" do
+    opts = Plug.Session.init(store: ProcessStore, key: "foobar")
+
+    conn = conn(:get, "/") |> fetch_cookies
+    conn = Plug.Session.call(conn, opts) |> fetch_session
+    conn = conn |> put_session(:foo, "bar") |> put_session(:bar, "foo")
+    conn = send_resp(conn, 200, "")
+
+    conn = conn(:get, "/") |> recycle_cookies(conn)
+    conn = init_test_session(conn, bar: "bar", other: "other")
+    conn = Plug.Session.call(conn, opts) |> fetch_session
+
+    assert get_session(conn, :foo) == "bar"
+    assert get_session(conn, :other) == "other"
+    assert get_session(conn, :bar) == "bar"
+  end
 end