Better port validation

Author: danschultzer

CHANGELOG.md

@@ -1,3 +1,7 @@
+## v0.1.7 (TBA)
+
+- The specified port is checked to ensure is in valid range
+
 ## v0.1.6 (2022-09-22)
 
 - Added suspended routes and web socket handlers to error messages

lib/test_server.ex

@@ -72,7 +72,7 @@ defmodule TestServer do
 
   defp raise_start_failure({:error, error}) do
     raise """
-    EXIT when starting #{__MODULE__.Instance}:
+    EXIT when starting #{inspect(__MODULE__.Instance)}:
 
     #{Exception.format_exit(error)}
     """

lib/test_server/plug_cowboy.ex

@@ -49,13 +49,17 @@ defmodule TestServer.Plug.Cowboy do
         port -> {port, []}
       end
 
-    unless is_integer(port), do: raise("Invalid port, got: #{inspect(port)}")
-
-    {:ok, socket} = :gen_tcp.listen(port, options)
-    {:ok, port} = :inet.port(socket)
-    true = :erlang.port_close(socket)
-
-    port
+    unless is_integer(port) and port >= 0 and port <= 65_535,
+      do: raise("Invalid port, got: #{inspect(port)}")
+
+    with {:ok, socket} <- :gen_tcp.listen(port, options),
+         {:ok, port} <- :inet.port(socket),
+         true <- :erlang.port_close(socket) do
+      port
+    else
+      {:error, error} ->
+        raise("Could not listen to port #{inspect(port)}, because: #{inspect(error)}")
+    end
   end
 
   @impl true

test/test_server_test.exs

@@ -11,6 +11,15 @@ defmodule TestServerTest do
       assert_raise RuntimeError, ~r/Invalid port, got: :invalid/, fn ->
         TestServer.start(port: :invalid)
       end
+
+      assert_raise RuntimeError, ~r/Invalid port, got: 65536/, fn ->
+        TestServer.start(port: 65_536)
+      end
+
+      assert_raise RuntimeError, ~r/Could not listen to port 4444, because: :eaddrinuse/, fn ->
+        TestServer.start(port: 4444)
+        TestServer.start(port: 4444)
+      end
     end
 
     test "with invalid scheme" do