make riak_kv_wterl_backend start the wterl app

src/riak_kv_wterl_backend.erl

@@ -87,6 +87,17 @@ start(Partition, Config) ->
             lager:error("Failed to create wterl dir: data_root is not set"),
             {error, data_root_unset};
         DataRoot ->
+            AppStart = case application:start(wterl) of
+                           ok ->
+                               ok;
+                           {error, {already_started, _}} ->
+                               ok;
+                           {error, Reason} ->
+                               lager:error("Failed to start wterl: ~p", [Reason]),
+                               {error, Reason}
+                       end,
+            case AppStart of
+                ok ->
                     ok = filelib:ensure_dir(filename:join(DataRoot, "x")),
                     case wterl_conn:open(DataRoot) of
                         {ok, ConnRef} ->
@@ -100,10 +111,13 @@ start(Partition, Config) ->
                                         table=Table,
                                         session=SRef,
                                         partition=Partition}};
-                {error, Reason} ->
+                        {error, ConnReason}=ConnError ->
                             lager:error("Failed to start wterl backend: ~p\n",
-                                [Reason]),
-                    {error, Reason}
+                                        [ConnReason]),
+                            ConnError
+                    end;
+                Error ->
+                    Error
             end
     end.
 
@@ -425,35 +439,13 @@ fetch_status(Cursor, {ok, Stat}, Acc) ->
 -ifdef(TEST).
 
 simple_test_() ->
-    {spawn, [{setup, SF, CF, TF}]} = riak_kv_backend:standard_test(?MODULE, []),
-    {setup,
-     fun() ->
     ?assertCmd("rm -rf test/wterl-backend"),
     application:set_env(wterl, data_root, "test/wterl-backend"),
-             application:start(wterl),
-             SF()
-     end,
-     fun(X) ->
-             CF(X),
-             application:stop(wterl)
-     end,
-     fun(X) -> TF(X) end}.
+    riak_kv_backend:standard_test(?MODULE, []).
 
 custom_config_test_() ->
-    {spawn, [{setup, SF, CF, TF}]} = riak_kv_backend:standard_test(
-                                       ?MODULE,
-                                       [{data_root, "test/wterl-backend"}]),
-    {setup,
-     fun() ->
     ?assertCmd("rm -rf test/wterl-backend"),
     application:set_env(wterl, data_root, ""),
-             application:start(wterl),
-             SF()
-     end,
-     fun(X) ->
-             CF(X),
-             application:stop(wterl)
-     end,
-     fun(X) -> TF(X) end}.
+    riak_kv_backend:standard_test(?MODULE, [{data_root, "test/wterl-backend"}]).
 
 -endif.

src/wterl_conn.erl

@@ -170,8 +170,12 @@ simple_test_() ->
        fun() ->
                ?assertCmd("rm -rf " ++ ?DATADIR),
                ?assertMatch(ok, filelib:ensure_dir(filename:join(?DATADIR, "x"))),
-               {ok, Pid} = start_link(),
+               case start_link() of
+                   {ok, Pid} ->
+                       Pid;
+                   {error, {already_started, Pid}} ->
                        Pid
+               end
        end,
        fun(_) ->
                stop()