add test verifying client works

config/config.exs

@@ -7,7 +7,8 @@
 # General application configuration
 import Config
 
-config :docker_engine_api, base_url: "http://localhost/v1.43"
+config :tesla, DockerEngineAPI.Connection,
+  adapter: Tesla.Adapter.Hackney
 
 # Import environment specific config. This must remain at the bottom
 # of this file so it overrides the configuration defined above.

lib/docker_engine_api/connection.ex

@@ -48,7 +48,7 @@ defmodule DockerEngineAPI.Connection do
   """
   @spec new() :: Tesla.Env.client()
   def new do
-    Tesla.client(middleware(), Tesla.Adapter.Hackney)
+    Tesla.client(middleware(), adapter())
   end
 
   @doc """
@@ -67,7 +67,7 @@ defmodule DockerEngineAPI.Connection do
   def new(options) when is_list(options) do
     options
     |> middleware()
-    |> Tesla.client(Tesla.Adapter.Hackney)
+    |> Tesla.client(adapter())
   end
 
 
@@ -85,7 +85,7 @@ defmodule DockerEngineAPI.Connection do
         Application.get_env(:docker_engine_api, :base_url, @default_base_url)
       )
 
-    tesla_options = Application.get_env(:tesla, __MODULE__, [])
+    tesla_options = get_tesla_options()
     middleware = Keyword.get(tesla_options, :middleware, [])
     json_engine = Keyword.get(tesla_options, :json, Jason)
 
@@ -109,4 +109,15 @@ defmodule DockerEngineAPI.Connection do
       | middleware
     ]
   end
+
+
+  def get_tesla_options, do: Application.get_env(:tesla, __MODULE__, [])
+
+  @doc """
+  Returns the default adapter for this API.
+  """
+  def adapter do
+    get_tesla_options()
+    |> Keyword.get(:adapter, nil)
+  end
 end

test/connection_test.exs

@@ -0,0 +1,11 @@
+defmodule DockerEngineAPI.ConnectionTest do
+  use ExUnit.Case
+
+  test "can list images" do
+    {:ok, list} = DockerEngineAPI.Connection.new(
+      base_url: "http+unix://%2Fvar%2Frun%2Fdocker.sock/v1.43"
+    )
+    |> DockerEngineAPI.Api.Image.image_list()
+    assert is_list(list)
+  end
+end