1 files changed, 18 insertions, 12 deletions
diff --git a/erts/emulator/test/port_SUITE.erl b/erts/emulator/test/port_SUITE.erl
index 3d0509a28c..f2a7ddef2c 100644
--- a/erts/emulator/test/port_SUITE.erl
+++ b/erts/emulator/test/port_SUITE.erl
@@ -385,27 +385,33 @@ input_only(Config) when is_list(Config) ->
 output_only(Config) when is_list(Config) ->
     Dog = test_server:timetrap(test_server:seconds(100)),
     Dir = ?config(priv_dir, Config),
+
+    %% First we test that the port program gets the data
     Filename = filename:join(Dir, "output_only_stream"),
-    output_and_verify(Config, Filename, "-h0",
-          	    random_packet(35777, "echo")),
+    Data = random_packet(35777, "echo"),
+    output_and_verify(Config, ["-h0 -o", Filename], Data),
+    Wait_time = 500,
+    test_server:sleep(Wait_time),
+    {ok, Written} = file:read_file(Filename),
+    Data = binary_to_list(Written),
+
+    %% Then we test that any writes to stdout from
+    %% the port program is not sent to erlang
+    output_and_verify(Config, ["-h0"], Data),
+
     test_server:timetrap_cancel(Dog),
     ok.
 
-output_and_verify(Config, Filename, Options, Data) ->
+output_and_verify(Config, Options, Data) ->
     PortTest = port_test(Config),
-    Command = lists:concat([PortTest, " ",
-          		  Options, " -o", Filename]),
+    Command = lists:concat([PortTest, " " | Options]),
     Port = open_port({spawn, Command}, [out]),
     Port ! {self(), {command, Data}},
     Port ! {self(), close},
     receive
-        {Port, closed} -> ok
-    end,
-    Wait_time = 500,
-    test_server:sleep(Wait_time),
-    {ok, Written} = file:read_file(Filename),
-    Data = binary_to_list(Written),
-    ok.
+        {Port, closed} -> ok;
+        Msg -> ct:fail({received_unexpected_message, Msg})
+    end.
 
 %% Test that receiving several packages written in the same
 %% write operation works.