refactor(dnsx): prepare for merging with netxlite (#515)

Part of https://github.com/ooni/probe/issues/1591

internal/netxlite/dnsx/mocks/roundtripper_test.go

@@ -1,73 +0,0 @@
-package mocks
-
-import (
-	"context"
-	"errors"
-	"testing"
-
-	"github.com/ooni/probe-cli/v3/internal/atomicx"
-)
-
-func TestRoundTripper(t *testing.T) {
-	t.Run("RoundTrip", func(t *testing.T) {
-		expected := errors.New("mocked error")
-		txp := &RoundTripper{
-			MockRoundTrip: func(ctx context.Context, query []byte) ([]byte, error) {
-				return nil, expected
-			},
-		}
-		resp, err := txp.RoundTrip(context.Background(), make([]byte, 16))
-		if !errors.Is(err, expected) {
-			t.Fatal("not the error we expected", err)
-		}
-		if resp != nil {
-			t.Fatal("expected nil response here")
-		}
-	})
-
-	t.Run("RequiresPadding", func(t *testing.T) {
-		txp := &RoundTripper{
-			MockRequiresPadding: func() bool {
-				return true
-			},
-		}
-		if txp.RequiresPadding() != true {
-			t.Fatal("unexpected result")
-		}
-	})
-
-	t.Run("Network", func(t *testing.T) {
-		txp := &RoundTripper{
-			MockNetwork: func() string {
-				return "antani"
-			},
-		}
-		if txp.Network() != "antani" {
-			t.Fatal("unexpected result")
-		}
-	})
-
-	t.Run("Address", func(t *testing.T) {
-		txp := &RoundTripper{
-			MockAddress: func() string {
-				return "mascetti"
-			},
-		}
-		if txp.Address() != "mascetti" {
-			t.Fatal("unexpected result")
-		}
-	})
-
-	t.Run("CloseIdleConnections", func(t *testing.T) {
-		called := &atomicx.Int64{}
-		txp := &RoundTripper{
-			MockCloseIdleConnections: func() {
-				called.Add(1)
-			},
-		}
-		txp.CloseIdleConnections()
-		if called.Load() != 1 {
-			t.Fatal("not called")
-		}
-	})
-}