Ensure connection errors return the expected error tuple

lib/tesla/adapter/mint.ex

@@ -176,8 +176,15 @@ if Code.ensure_loaded?(Mint.HTTP) do
       end
     end
 
-    defp make_request(conn, method, path, headers, body),
-      do: HTTP.request(conn, method, path, headers, body)
+    defp make_request(conn, method, path, headers, body) do
+      case HTTP.request(conn, method, path, headers, body) do
+        {:ok, conn, ref} ->
+          {:ok, conn, ref}
+
+        {:error, _conn, error} ->
+          {:error, error}
+      end
+    end
 
     defp stream_request(conn, ref, fun) do
       case next_chunk(fun) do

test/tesla/adapter/mint_test.exs

@@ -11,7 +11,7 @@ defmodule Tesla.Adapter.MintTest do
       cacertfile: Path.join([to_string(:code.priv_dir(:httparrot)), "/ssl/server-ca.crt"])
     ]
 
-  test "Delay request" do
+  test "timeout request" do
     request = %Env{
       method: :head,
       url: "#{@http}/delay/1"
@@ -179,6 +179,26 @@ defmodule Tesla.Adapter.MintTest do
       assert conn.state == :closed
     end
 
+    test "body_as :plain - returns error tuple matching the specification when connection is closed",
+         %{conn: conn, original: original} do
+      request = %Env{
+        method: :get,
+        url: "#{@http}/stream-bytes/10"
+      }
+
+      assert {:ok, %Env{} = response} =
+               call(request, conn: conn, original: original, close_conn: false)
+
+      assert response.status == 200
+      assert byte_size(response.body) == 16
+
+      {:ok, conn} = Tesla.Adapter.Mint.close(conn)
+      assert conn.state == :closed
+
+      assert {:error, %Mint.HTTPError{reason: :closed, module: Mint.HTTP1}} =
+               call(request, conn: conn, original: original, close_conn: false)
+    end
+
     test "body_as :stream", %{conn: conn, original: original} do
       request = %Env{
         method: :get,