ML-21: Classify API errors as transient vs permanent

test/discogs_test.exs

@@ -1,6 +1,7 @@
 defmodule DiscogsTest do
   use ExUnit.Case, async: true
 
+  alias Discogs.API.ErrorResponse
   alias Discogs.Fixtures
 
   describe "get_artist/1" do
@@ -16,5 +17,47 @@ defmodule DiscogsTest do
 
       assert {:ok, expected_info} == Discogs.get_artist(discogs_id)
     end
+
+    @tag :capture_log
+    test "returns a rate-limit ErrorResponse on 429" do
+      Req.Test.stub(Discogs.API, fn conn ->
+        conn
+        |> Plug.Conn.put_status(429)
+        |> Req.Test.json(%{"message" => "You are making requests too quickly."})
+      end)
+
+      assert {:error, %ErrorResponse{} = err} = Discogs.get_artist("1")
+      assert err.status == 429
+      assert err.kind == :rate_limit
+      assert ErrorResponse.retryable?(err)
+    end
+
+    @tag :capture_log
+    test "returns a not-found ErrorResponse on 404" do
+      Req.Test.stub(Discogs.API, fn conn ->
+        conn
+        |> Plug.Conn.put_status(404)
+        |> Req.Test.json(%{"message" => "The requested resource was not found."})
+      end)
+
+      assert {:error, %ErrorResponse{kind: :not_found} = err} =
+               Discogs.get_artist("1")
+
+      refute ErrorResponse.retryable?(err)
+    end
+
+    @tag :capture_log
+    test "returns a server-error ErrorResponse on 500" do
+      Req.Test.stub(Discogs.API, fn conn ->
+        conn
+        |> Plug.Conn.put_status(500)
+        |> Req.Test.json(%{"message" => "Internal server error"})
+      end)
+
+      assert {:error, %ErrorResponse{kind: :server_error} = err} =
+               Discogs.get_artist("1")
+
+      assert ErrorResponse.retryable?(err)
+    end
   end
 end