chore(general): enable forcetypeassert linter (#4624)

- enable `forcetypeassert` linter in non-test files - add `//nolint` annotations - add `testutil.EnsureType` helper for type assertions - enable `forcetypeassert` linter in test files
2025-12-23 22:57:50 -05:00 · 2025-05-31 23:17:38 -07:00
parent 44566ec50c
commit d91a5a8f94
32 changed files with 156 additions and 99 deletions
--- a/.golangci.yml
+++ b/.golangci.yml
@@ -84,7 +84,6 @@ linters:
  default: all
  disable:
    - exhaustruct
-    - forcetypeassert
    - funcorder
    - gochecknoglobals
    - gochecknoinits
@@ -120,7 +119,6 @@ linters:
          - contextcheck
          - errcheck
          - errchkjson
-          - forcetypeassert
          - funlen
          - gochecknoglobals
          - gocognit
--- a/cli/command_repository_set_parameters_test.go
+++ b/cli/command_repository_set_parameters_test.go
@@ -20,9 +20,9 @@ func (s *formatSpecificTestSuite) setupInMemoryRepo(t *testing.T) *testenv.CLITe
 	runner := testenv.NewInProcRunner(t)
 	env := testenv.NewCLITest(t, s.formatFlags, runner)
 	st := repotesting.NewReconnectableStorage(t, blobtesting.NewVersionedMapStorage(nil))
+	o := testutil.EnsureType[*repotesting.ReconnectableStorageOptions](t, st.ConnectionInfo().Config)

-	env.RunAndExpectSuccess(t, "repo", "create", "in-memory", "--uuid",
-		st.ConnectionInfo().Config.(*repotesting.ReconnectableStorageOptions).UUID)
+	env.RunAndExpectSuccess(t, "repo", "create", "in-memory", "--uuid", o.UUID)

 	return env
 }
--- a/internal/blobtesting/eventually_consistent.go
+++ b/internal/blobtesting/eventually_consistent.go
@@ -255,12 +255,12 @@ func (s *eventuallyConsistentStorage) ListBlobs(ctx context.Context, prefix blob

 	// process recently deleted items and resurrect them with some probability
 	s.recentlyDeleted.Range(func(key, value any) bool {
-		blobID := key.(blob.ID)
+		blobID := key.(blob.ID) //nolint:forcetypeassert
 		if !strings.HasPrefix(string(blobID), string(prefix)) {
 			return true
 		}

-		bm := value.(blob.Metadata)
+		bm := value.(blob.Metadata) //nolint:forcetypeassert
 		if age := now.Sub(bm.Timestamp); s.shouldApplyInconsistency(ctx, age, "resurrect recently deleted "+string(bm.BlobID)) {
 			if resultErr = callback(bm); resultErr != nil {
 				return false
--- a/internal/cache/content_cache_concurrency_test.go
+++ b/internal/cache/content_cache_concurrency_test.go
@@ -15,6 +15,7 @@
 	"github.com/kopia/kopia/internal/cache"
 	"github.com/kopia/kopia/internal/gather"
 	"github.com/kopia/kopia/internal/testlogging"
+	"github.com/kopia/kopia/internal/testutil"
 	"github.com/kopia/kopia/repo/blob"
 )

@@ -89,7 +90,7 @@ func testContentCachePrefetchBlocksGetContent(t *testing.T, newCache newContentC
 	faulty := blobtesting.NewFaultyStorage(underlying)

 	cacheData := blobtesting.DataMap{}
-	metadataCacheStorage := blobtesting.NewMapStorage(cacheData, nil, nil).(cache.Storage)
+	metadataCacheStorage := testutil.EnsureType[cache.Storage](t, blobtesting.NewMapStorage(cacheData, nil, nil))

 	dataCache, err := newCache(ctx, faulty, metadataCacheStorage)
 	require.NoError(t, err)
@@ -157,7 +158,7 @@ func testGetContentForDifferentContentIDsExecutesInParallel(t *testing.T, newCac
 	faulty := blobtesting.NewFaultyStorage(underlying)

 	cacheData := blobtesting.DataMap{}
-	metadataCacheStorage := blobtesting.NewMapStorage(cacheData, nil, nil).(cache.Storage)
+	metadataCacheStorage := testutil.EnsureType[cache.Storage](t, blobtesting.NewMapStorage(cacheData, nil, nil))

 	dataCache, err := newCache(ctx, faulty, metadataCacheStorage)
 	require.NoError(t, err)
@@ -203,7 +204,7 @@ func testGetContentForDifferentBlobsExecutesInParallel(t *testing.T, newCache ne
 	faulty := blobtesting.NewFaultyStorage(underlying)

 	cacheData := blobtesting.DataMap{}
-	metadataCacheStorage := blobtesting.NewMapStorage(cacheData, nil, nil).(cache.Storage)
+	metadataCacheStorage := testutil.EnsureType[cache.Storage](t, blobtesting.NewMapStorage(cacheData, nil, nil))

 	dataCache, err := newCache(ctx, faulty, metadataCacheStorage)
 	require.NoError(t, err)
@@ -251,7 +252,7 @@ func testGetContentRaceFetchesOnce(t *testing.T, newCache newContentCacheFunc) {
 	faulty := blobtesting.NewFaultyStorage(underlying)

 	cacheData := blobtesting.DataMap{}
-	metadataCacheStorage := blobtesting.NewMapStorage(cacheData, nil, nil).(cache.Storage)
+	metadataCacheStorage := testutil.EnsureType[cache.Storage](t, blobtesting.NewMapStorage(cacheData, nil, nil))

 	dataCache, err := newCache(ctx, faulty, metadataCacheStorage)
 	require.NoError(t, err)
--- a/internal/cache/content_cache_data_test.go
+++ b/internal/cache/content_cache_data_test.go
@@ -9,6 +9,7 @@
 	"github.com/kopia/kopia/internal/cache"
 	"github.com/kopia/kopia/internal/gather"
 	"github.com/kopia/kopia/internal/testlogging"
+	"github.com/kopia/kopia/internal/testutil"
 	"github.com/kopia/kopia/repo/blob"
 )

@@ -19,7 +20,7 @@ func TestContentCacheForData(t *testing.T) {
 	underlying := blobtesting.NewMapStorage(underlyingData, nil, nil)

 	cacheData := blobtesting.DataMap{}
-	cacheStorage := blobtesting.NewMapStorage(cacheData, nil, nil).(cache.Storage)
+	cacheStorage := testutil.EnsureType[cache.Storage](t, blobtesting.NewMapStorage(cacheData, nil, nil))

 	dataCache, err := cache.NewContentCache(ctx, underlying, cache.Options{
 		Storage:    cacheStorage,
--- a/internal/cache/content_cache_test.go
+++ b/internal/cache/content_cache_test.go
@@ -108,13 +108,13 @@ func verifyCacheExpiration(t *testing.T, sweepSettings cache.SweepSettings, want

 		return currentTime
 	}
-	cacheStorage := blobtesting.NewMapStorage(cacheData, nil, movingTimeFunc)

+	cacheStorage := testutil.EnsureType[cache.Storage](t, blobtesting.NewMapStorage(cacheData, nil, movingTimeFunc))
 	underlyingStorage := newUnderlyingStorageForContentCacheTesting(t)

 	ctx := testlogging.Context(t)
 	cc, err := cache.NewContentCache(ctx, underlyingStorage, cache.Options{
-		Storage: cacheStorage.(cache.Storage),
+		Storage: cacheStorage,
 		Sweep:   sweepSettings,
 		TimeNow: movingTimeFunc,
 	}, nil)
--- a/internal/cache/persistent_lru_cache_test.go
+++ b/internal/cache/persistent_lru_cache_test.go
@@ -25,7 +25,7 @@ func TestPersistentLRUCache(t *testing.T) {

 	const maxSizeBytes = 1000

-	cs := blobtesting.NewMapStorageWithLimit(blobtesting.DataMap{}, nil, nil, maxSizeBytes).(cache.Storage)
+	cs := testutil.EnsureType[cache.Storage](t, blobtesting.NewMapStorageWithLimit(blobtesting.DataMap{}, nil, nil, maxSizeBytes))

 	pc, err := cache.NewPersistentCache(ctx, "testing", cs, cacheprot.ChecksumProtection([]byte{1, 2, 3}), cache.SweepSettings{
 		MaxSizeBytes:   maxSizeBytes,
--- a/internal/connection/reconnector_test.go
+++ b/internal/connection/reconnector_test.go
@@ -13,6 +13,7 @@

 	"github.com/kopia/kopia/internal/connection"
 	"github.com/kopia/kopia/internal/testlogging"
+	"github.com/kopia/kopia/internal/testutil"
 )

 var (
@@ -74,7 +75,8 @@ func TestConnection(t *testing.T) {
 	r := connection.NewReconnector(fc)

 	v, err := connection.UsingConnection(ctx, r, "first", func(cli connection.Connection) (any, error) {
-		require.EqualValues(t, 1, cli.(*fakeConnection).id)
+		require.EqualValues(t, 1, testutil.EnsureType[*fakeConnection](t, cli).id)
+
 		return "foo", nil
 	})

@@ -84,20 +86,22 @@ func TestConnection(t *testing.T) {
 	cnt := 0

 	r.UsingConnectionNoResult(ctx, "second", func(cli connection.Connection) error {
-		t.Logf("second called with %v", cli.(*fakeConnection).id)
+		fcon := testutil.EnsureType[*fakeConnection](t, cli)
+
+		t.Log("second called with", fcon.id)

 		// still using connection # 1
 		if cnt == 0 {
 			cnt++

-			require.EqualValues(t, 1, cli.(*fakeConnection).id)
+			require.EqualValues(t, 1, fcon.id)

-			cli.(*fakeConnection).isClosed = true
+			fcon.isClosed = true

 			return errFakeConnectionFailed
 		}

-		require.EqualValues(t, 2, cli.(*fakeConnection).id)
+		require.EqualValues(t, 2, fcon.id)

 		return nil
 	})
@@ -105,8 +109,10 @@ func TestConnection(t *testing.T) {
 	require.EqualValues(t, 2, fc.nextConnectionID.Load())

 	r.UsingConnectionNoResult(ctx, "third", func(cli connection.Connection) error {
-		t.Logf("third called with %v", cli.(*fakeConnection).id)
-		require.EqualValues(t, 2, cli.(*fakeConnection).id)
+		id0 := testutil.EnsureType[*fakeConnection](t, cli).id
+
+		t.Log("third called with", id0)
+		require.EqualValues(t, 2, id0)

 		return nil
 	})
@@ -114,12 +120,16 @@ func TestConnection(t *testing.T) {
 	require.EqualValues(t, 2, fc.nextConnectionID.Load())

 	r.UsingConnectionNoResult(ctx, "parallel-1", func(cli connection.Connection) error {
-		t.Logf("parallel-1 called with %v", cli.(*fakeConnection).id)
-		require.EqualValues(t, 2, cli.(*fakeConnection).id)
+		id1 := testutil.EnsureType[*fakeConnection](t, cli).id
+
+		t.Log("parallel-1 called with", id1)
+		require.EqualValues(t, 2, id1)

 		r.UsingConnectionNoResult(ctx, "parallel-2", func(cli connection.Connection) error {
-			t.Logf("parallel-2 called with %v", cli.(*fakeConnection).id)
-			require.EqualValues(t, 2, cli.(*fakeConnection).id)
+			id2 := testutil.EnsureType[*fakeConnection](t, cli).id
+
+			t.Log("parallel-2 called with", id2)
+			require.EqualValues(t, 2, id2)

 			return nil
 		})
@@ -130,8 +140,10 @@ func TestConnection(t *testing.T) {
 	r.CloseActiveConnection(ctx)

 	require.NoError(t, r.UsingConnectionNoResult(ctx, "fourth", func(cli connection.Connection) error {
-		t.Logf("fourth called with %v", cli.(*fakeConnection).id)
-		require.EqualValues(t, 3, cli.(*fakeConnection).id)
+		id3 := testutil.EnsureType[*fakeConnection](t, cli).id
+
+		t.Log("fourth called with", id3)
+		require.EqualValues(t, 3, id3)

 		return nil
 	}))
@@ -148,8 +160,10 @@ func TestConnection(t *testing.T) {
 	fc.nextError = errFakeConnectionFailed

 	require.NoError(t, r.UsingConnectionNoResult(ctx, "sixth", func(cli connection.Connection) error {
-		t.Logf("sixth called with %v", cli.(*fakeConnection).id)
-		require.EqualValues(t, 4, cli.(*fakeConnection).id)
+		id4 := testutil.EnsureType[*fakeConnection](t, cli).id
+
+		t.Log("sixth called with", id4)
+		require.EqualValues(t, 4, id4)

 		return nil
 	}))
@@ -159,7 +173,7 @@ func TestConnection(t *testing.T) {
 	eg.Go(func() error {
 		return r.UsingConnectionNoResult(ctx, "parallel-a", func(cli connection.Connection) error {
 			time.Sleep(500 * time.Millisecond)
-			t.Logf("parallel-a called with %v", cli.(*fakeConnection).id)
+			t.Log("parallel-a called with", testutil.EnsureType[*fakeConnection](t, cli).id)

 			return nil
 		})
@@ -167,7 +181,7 @@ func TestConnection(t *testing.T) {
 	eg.Go(func() error {
 		return r.UsingConnectionNoResult(ctx, "parallel-b", func(cli connection.Connection) error {
 			time.Sleep(300 * time.Millisecond)
-			t.Logf("parallel-b called with %v", cli.(*fakeConnection).id)
+			t.Log("parallel-b called with", testutil.EnsureType[*fakeConnection](t, cli).id)

 			return nil
 		})
@@ -175,7 +189,7 @@ func TestConnection(t *testing.T) {
 	eg.Go(func() error {
 		return r.UsingConnectionNoResult(ctx, "parallel-c", func(cli connection.Connection) error {
 			time.Sleep(100 * time.Millisecond)
-			t.Logf("parallel-c called with %v", cli.(*fakeConnection).id)
+			t.Log("parallel-c called with", testutil.EnsureType[*fakeConnection](t, cli).id)

 			return nil
 		})
--- a/internal/epoch/epoch_manager_test.go
+++ b/internal/epoch/epoch_manager_test.go
@@ -862,7 +862,7 @@ func verifySequentialWrites(t *testing.T, te *epochManagerTestEnv) {
 func TestIndexEpochManager_Disabled(t *testing.T) {
 	te := newTestEnv(t)

-	te.mgr.paramProvider.(parameterProvider).Enabled = false
+	testutil.EnsureType[parameterProvider](t, te.mgr.paramProvider).Enabled = false

 	_, err := te.mgr.Current(testlogging.Context(t))
 	require.Error(t, err)
--- a/internal/fusemount/fusefs.go
+++ b/internal/fusemount/fusefs.go
@@ -73,7 +73,7 @@ type fuseFileNode struct {
 }

 func (f *fuseFileNode) Open(ctx context.Context, _ uint32) (gofusefs.FileHandle, uint32, syscall.Errno) {
-	reader, err := f.entry.(fs.File).Open(ctx)
+	reader, err := f.entry.(fs.File).Open(ctx) //nolint:forcetypeassert
 	if err != nil {
 		log(ctx).Errorf("error opening %v: %v", f.entry.Name(), err)

@@ -198,7 +198,7 @@ type fuseSymlinkNode struct {
 }

 func (sl *fuseSymlinkNode) Readlink(ctx context.Context) ([]byte, syscall.Errno) {
-	v, err := sl.entry.(fs.Symlink).Readlink(ctx)
+	v, err := sl.entry.(fs.Symlink).Readlink(ctx) //nolint:forcetypeassert
 	if err != nil {
 		log(ctx).Errorf("error reading symlink %v: %v", sl.entry.Name(), err)
 		return nil, syscall.EIO
--- a/internal/gather/gather_bytes_test.go
+++ b/internal/gather/gather_bytes_test.go
@@ -10,6 +10,8 @@

 	"github.com/pkg/errors"
 	"github.com/stretchr/testify/require"
+
+	"github.com/kopia/kopia/internal/testutil"
 )

 var sample1 = []byte("hello! how are you? nice to meet you.")
@@ -236,7 +238,7 @@ func TestGatherBytesReaderAtErrorResponses(t *testing.T) {
 			defer reader.Close() //nolint:errcheck

 			// get the reader as a ReaderAt
-			readerAt := reader.(io.ReaderAt)
+			readerAt := testutil.EnsureType[io.ReaderAt](t, reader)

 			// make an output buffer of the required length
 			bs := make([]byte, tc.inBsLen)
--- a/internal/listcache/listcache_test.go
+++ b/internal/listcache/listcache_test.go
@@ -11,6 +11,7 @@
 	"github.com/kopia/kopia/internal/faketime"
 	"github.com/kopia/kopia/internal/gather"
 	"github.com/kopia/kopia/internal/testlogging"
+	"github.com/kopia/kopia/internal/testutil"
 	"github.com/kopia/kopia/repo/blob"
 )

@@ -22,7 +23,9 @@ func TestListCache(t *testing.T) {
 	cacheTime := faketime.NewTimeAdvance(time.Date(2020, 1, 2, 3, 4, 5, 6, time.UTC))
 	cachest := blobtesting.NewMapStorage(blobtesting.DataMap{}, nil, cacheTime.NowFunc())

-	lc := NewWrapper(realStorage, cachest, []blob.ID{"n", "xe", "xb"}, []byte("hmac-secret"), 1*time.Minute).(*listCacheStorage)
+	w := NewWrapper(realStorage, cachest, []blob.ID{"n", "xe", "xb"}, []byte("hmac-secret"), 1*time.Minute)
+	lc := testutil.EnsureType[*listCacheStorage](t, w)
+
 	lc.cacheTimeFunc = cacheTime.NowFunc()

 	ctx := testlogging.Context(t)
--- a/internal/ownwrites/ownwrites_test.go
+++ b/internal/ownwrites/ownwrites_test.go
@@ -10,6 +10,7 @@
 	"github.com/kopia/kopia/internal/faketime"
 	"github.com/kopia/kopia/internal/gather"
 	"github.com/kopia/kopia/internal/testlogging"
+	"github.com/kopia/kopia/internal/testutil"
 	"github.com/kopia/kopia/repo/blob"
 )

@@ -23,7 +24,7 @@ func TestOwnWrites(t *testing.T) {

 	ec := blobtesting.NewEventuallyConsistentStorage(realStorage, 1*time.Hour, realStorageTime.NowFunc())
 	ow := NewWrapper(ec, cachest, []blob.ID{"n"}, testCacheDuration)
-	ow.(*CacheStorage).cacheTimeFunc = cacheTime.NowFunc()
+	testutil.EnsureType[*CacheStorage](t, ow).cacheTimeFunc = cacheTime.NowFunc()

 	ctx := testlogging.Context(t)

--- a/internal/repotesting/reconnectable_storage.go
+++ b/internal/repotesting/reconnectable_storage.go
@@ -67,7 +67,7 @@ func New(ctx context.Context, opt *ReconnectableStorageOptions, isCreate bool) (
 		return nil, errors.Errorf("reconnectable storage not found: %v", opt.UUID)
 	}

-	return v.(blob.Storage), nil
+	return v.(blob.Storage), nil //nolint:forcetypeassert
 }

 func init() {
--- a/internal/repotesting/repotesting.go
+++ b/internal/repotesting/repotesting.go
@@ -45,7 +45,7 @@ type Options struct {

 // RepositoryMetrics returns metrics.Registry associated with a repository.
 func (e *Environment) RepositoryMetrics() *metrics.Registry {
-	return e.Repository.(interface {
+	return e.Repository.(interface { //nolint:forcetypeassert
 		Metrics() *metrics.Registry
 	}).Metrics()
 }
@@ -53,7 +53,7 @@ func (e *Environment) RepositoryMetrics() *metrics.Registry {
 // RootStorage returns the base storage map that implements the base in-memory
 // map at the base of all storage wrappers on top.
 func (e *Environment) RootStorage() blob.Storage {
-	return e.st.(reconnectableStorage).Storage
+	return e.st.(reconnectableStorage).Storage //nolint:forcetypeassert
 }

 // setup sets up a test environment.
@@ -126,7 +126,7 @@ func (e *Environment) setup(tb testing.TB, version format.Version, opts ...Optio

 	e.Repository = rep

-	_, e.RepositoryWriter, err = rep.(repo.DirectRepository).NewDirectWriter(ctx, repo.WriteSessionOptions{Purpose: "test"})
+	_, e.RepositoryWriter, err = testutil.EnsureType[repo.DirectRepository](tb, rep).NewDirectWriter(ctx, repo.WriteSessionOptions{Purpose: "test"})
 	require.NoError(tb, err)

 	tb.Cleanup(func() {
@@ -177,7 +177,7 @@ func (e *Environment) MustReopen(tb testing.TB, openOpts ...func(*repo.Options))

 	tb.Cleanup(func() { rep.Close(ctx) })

-	_, e.RepositoryWriter, err = rep.(repo.DirectRepository).NewDirectWriter(ctx, repo.WriteSessionOptions{Purpose: "test"})
+	_, e.RepositoryWriter, err = testutil.EnsureType[repo.DirectRepository](tb, rep).NewDirectWriter(ctx, repo.WriteSessionOptions{Purpose: "test"})
 	require.NoError(tb, err)
 }

--- a/internal/repotesting/repotesting_test.go
+++ b/internal/repotesting/repotesting_test.go
@@ -9,6 +9,7 @@
 	"github.com/kopia/kopia/internal/faketime"
 	"github.com/kopia/kopia/internal/gather"
 	"github.com/kopia/kopia/internal/mockfs"
+	"github.com/kopia/kopia/internal/testutil"
 	"github.com/kopia/kopia/repo"
 	"github.com/kopia/kopia/repo/content"
 	"github.com/kopia/kopia/snapshot"
@@ -27,7 +28,7 @@ func TestTimeFuncWiring(t *testing.T) {
 		t.Fatal("Failed to open repo:", err)
 	}

-	r0 := rep.(repo.DirectRepository)
+	r0 := testutil.EnsureType[repo.DirectRepository](t, rep)

 	_, env.RepositoryWriter, err = r0.NewDirectWriter(ctx, repo.WriteSessionOptions{Purpose: "test"})
 	require.NoError(t, err)
--- a/internal/testutil/testutil.go
+++ b/internal/testutil/testutil.go
@@ -177,3 +177,17 @@ func MustGetTotalDirSize(t *testing.T, dirpath string) int64 {

 	return total
 }
+
+// EnsureType asserts that v of type E.
+func EnsureType[E any](tb testing.TB, v any) E {
+	tb.Helper()
+
+	var e E
+
+	// require.IsType would not elide the forced type assertion
+	e, ok := v.(E)
+
+	require.Truef(tb, ok, "%T is not of type %T", v, e)
+
+	return e
+}
--- a/repo/blob/filesystem/filesystem_storage_test.go
+++ b/repo/blob/filesystem/filesystem_storage_test.go
@@ -102,7 +102,7 @@ func TestFileStorageTouch(t *testing.T) {
 		t.Errorf("unexpected result: %v %v", r, err)
 	}

-	fs := r.(*fsStorage)
+	fs := testutil.EnsureType[*fsStorage](t, r)
 	assertNoError(t, fs.PutBlob(ctx, t1, gather.FromSlice([]byte{1}), blob.PutOptions{}))
 	time.Sleep(2 * time.Second) // sleep a bit to accommodate Apple filesystems with low timestamp resolution
 	assertNoError(t, fs.PutBlob(ctx, t2, gather.FromSlice([]byte{1}), blob.PutOptions{}))
@@ -232,12 +232,20 @@ func TestFileStorage_GetMetadata_RetriesOnError(t *testing.T) {

 	require.NoError(t, st.PutBlob(ctx, "someblob1234567812345678", gather.FromSlice([]byte{1, 2, 3}), blob.PutOptions{}))

-	st.(*fsStorage).Impl.(*fsImpl).osi = osi
+	asFsImpl(t, st).osi = osi

 	_, err = st.GetMetadata(ctx, "someblob1234567812345678")
 	require.NoError(t, err)
 }

+func asFsImpl(t *testing.T, st blob.Storage) *fsImpl {
+	t.Helper()
+
+	fsSt := testutil.EnsureType[*fsStorage](t, st)
+
+	return testutil.EnsureType[*fsImpl](t, fsSt.Impl)
+}
+
 func TestFileStorage_PutBlob_RetriesOnErrors(t *testing.T) {
 	t.Parallel()

@@ -269,7 +277,7 @@ func TestFileStorage_PutBlob_RetriesOnErrors(t *testing.T) {
 	}, true)
 	require.NoError(t, err)

-	st.(*fsStorage).Impl.(*fsImpl).osi = osi
+	asFsImpl(t, st).osi = osi

 	defer st.Close(ctx)

@@ -310,7 +318,7 @@ func TestFileStorage_DeleteBlob_ErrorHandling(t *testing.T) {
 	}, true)
 	require.NoError(t, err)

-	st.(*fsStorage).Impl.(*fsImpl).osi = osi
+	asFsImpl(t, st).osi = osi

 	defer st.Close(ctx)

@@ -381,7 +389,7 @@ func TestFileStorage_ListBlobs_ErrorHandling(t *testing.T) {
 	}, true)
 	require.NoError(t, err)

-	st.(*fsStorage).Impl.(*fsImpl).osi = osi
+	asFsImpl(t, st).osi = osi

 	defer st.Close(ctx)

@@ -419,7 +427,7 @@ func TestFileStorage_TouchBlob_ErrorHandling(t *testing.T) {
 	}, true)
 	require.NoError(t, err)

-	st.(*fsStorage).Impl.(*fsImpl).osi = osi
+	asFsImpl(t, st).osi = osi

 	defer st.Close(ctx)

@@ -427,7 +435,7 @@ func TestFileStorage_TouchBlob_ErrorHandling(t *testing.T) {

 	osi.statRemainingErrors.Store(1)

-	_, err = st.(*fsStorage).TouchBlob(ctx, "someblob1234567812345678", 0)
+	_, err = testutil.EnsureType[*fsStorage](t, st).TouchBlob(ctx, "someblob1234567812345678", 0)
 	require.NoError(t, err)
 }

--- a/repo/blob/filesystem/filesystem_storage_unix_test.go
+++ b/repo/blob/filesystem/filesystem_storage_unix_test.go
@@ -33,9 +33,10 @@ func TestFileStorage_ESTALE_ErrorHandling(t *testing.T) {
 	}, true)
 	require.NoError(t, err)

-	st.(*fsStorage).Impl.(*fsImpl).osi = osi
+	fsi := asFsImpl(t, st)
+	fsi.osi = osi

-	require.False(t, st.(*fsStorage).Impl.(*fsImpl).isRetriable(syscall.ESTALE), "ESTALE should not be retryable")
+	require.False(t, fsi.isRetriable(syscall.ESTALE), "ESTALE should not be retryable")

 	defer st.Close(ctx)

--- a/repo/blob/registry_test.go
+++ b/repo/blob/registry_test.go
@@ -8,6 +8,7 @@

 	"github.com/stretchr/testify/require"

+	"github.com/kopia/kopia/internal/testutil"
 	"github.com/kopia/kopia/repo/blob"
 )

@@ -35,9 +36,11 @@ func TestRegistry(t *testing.T) {
 	}, true)

 	require.NoError(t, err)
-	require.IsType(t, (*myStorage)(nil), st)
-	require.Equal(t, 4, st.(*myStorage).cfg.Field)
-	require.True(t, st.(*myStorage).create)
+
+	mySt := testutil.EnsureType[*myStorage](t, st)
+
+	require.Equal(t, 4, mySt.cfg.Field)
+	require.True(t, mySt.create)

 	_, err = blob.NewStorage(context.Background(), blob.ConnectionInfo{
 		Type: "unknownstorage",
--- a/repo/blob/storage_extend_test.go
+++ b/repo/blob/storage_extend_test.go
@@ -11,6 +11,7 @@
 	"github.com/kopia/kopia/internal/blobtesting"
 	"github.com/kopia/kopia/internal/faketime"
 	"github.com/kopia/kopia/internal/repotesting"
+	"github.com/kopia/kopia/internal/testutil"
 	"github.com/kopia/kopia/repo"
 	"github.com/kopia/kopia/repo/blob"
 	"github.com/kopia/kopia/repo/encryption"
@@ -57,7 +58,7 @@ func (s *formatSpecificTestSuite) TestExtendBlobRetention(t *testing.T) {
 	}

 	lastBlobIdx := len(blobsBefore) - 1
-	st := env.RootStorage().(blobtesting.RetentionStorage)
+	st := testutil.EnsureType[blobtesting.RetentionStorage](t, env.RootStorage())

 	// Verify that file is locked
 	gotMode, expiry, err := st.GetRetention(ctx, blobsBefore[lastBlobIdx].BlobID)
--- a/repo/ecc/ecc_rs_crc_test.go
+++ b/repo/ecc/ecc_rs_crc_test.go
@@ -5,6 +5,7 @@

 	"github.com/stretchr/testify/require"

+	"github.com/kopia/kopia/internal/testutil"
 	"github.com/kopia/kopia/repo/encryption"
 )

@@ -114,7 +115,8 @@ func testRsCrc32ChangeInData(t *testing.T, opts *Options, originalSize, changedB

 	testPutAndGet(t, opts, originalSize, expectedEccSize, expectedSuccess,
 		func(impl encryption.Encryptor, data []byte) {
-			sizes := impl.(*ReedSolomonCrcECC).computeSizesFromOriginal(originalSize)
+			ecc := testutil.EnsureType[*ReedSolomonCrcECC](t, impl)
+			sizes := ecc.computeSizesFromOriginal(originalSize)
 			parity := sizes.ParityShards * (crcSize + sizes.ShardSize) * sizes.Blocks

 			for i := range changedBytes {
@@ -128,7 +130,8 @@ func testRsCrc32ChangeInDataCrc(t *testing.T, opts *Options, originalSize, chang

 	testPutAndGet(t, opts, originalSize, expectedEccSize, expectedSuccess,
 		func(impl encryption.Encryptor, data []byte) {
-			sizes := impl.(*ReedSolomonCrcECC).computeSizesFromOriginal(originalSize)
+			ecc := testutil.EnsureType[*ReedSolomonCrcECC](t, impl)
+			sizes := ecc.computeSizesFromOriginal(originalSize)
 			parity := sizes.ParityShards * (crcSize + sizes.ShardSize) * sizes.Blocks

 			for i := range changedBytes {
@@ -142,7 +145,8 @@ func testRsCrc32ChangeInParity(t *testing.T, opts *Options, originalSize, change

 	testPutAndGet(t, opts, originalSize, expectedEccSize, expectedSuccess,
 		func(impl encryption.Encryptor, data []byte) {
-			sizes := impl.(*ReedSolomonCrcECC).computeSizesFromOriginal(originalSize)
+			ecc := testutil.EnsureType[*ReedSolomonCrcECC](t, impl)
+			sizes := ecc.computeSizesFromOriginal(originalSize)

 			for i := range changedBytes {
 				flipByte(data, i*(crcSize+sizes.ShardSize)+crcSize)
@@ -155,7 +159,8 @@ func testRsCrc32ChangeInParityCrc(t *testing.T, opts *Options, originalSize, cha

 	testPutAndGet(t, opts, originalSize, expectedEccSize, expectedSuccess,
 		func(impl encryption.Encryptor, data []byte) {
-			sizes := impl.(*ReedSolomonCrcECC).computeSizesFromOriginal(originalSize)
+			ecc := testutil.EnsureType[*ReedSolomonCrcECC](t, impl)
+			sizes := ecc.computeSizesFromOriginal(originalSize)

 			for i := range changedBytes {
 				flipByte(data, i*(crcSize+sizes.ShardSize))
--- a/repo/format/upgrade_lock_test.go
+++ b/repo/format/upgrade_lock_test.go
@@ -171,7 +171,7 @@ func TestFormatUpgradeMultipleLocksRollback(t *testing.T) {
 	// second lock from a random owner
 	secondL := l.Clone()
 	secondL.OwnerID = "another-upgrade-owner"
-	_, err = secondWriter.(repo.DirectRepositoryWriter).FormatManager().SetUpgradeLockIntent(ctx, *secondL)
+	_, err = testutil.EnsureType[repo.DirectRepositoryWriter](t, secondWriter).FormatManager().SetUpgradeLockIntent(ctx, *secondL)
 	require.NoError(t, err)

 	// verify that we have two repository backups, the second one will contain
@@ -290,31 +290,33 @@ func(ctx context.Context, id blob.ID, _ *blob.PutOptions) error {
 	r, err := repo.Open(testlogging.Context(t), configFile, "password", &repo.Options{UpgradeOwnerID: "allowed-upgrade-owner"})
 	require.NoError(t, err)

-	_, err = r.(repo.DirectRepositoryWriter).FormatManager().SetUpgradeLockIntent(testlogging.Context(t), *faultyLock)
+	drw := testutil.EnsureType[repo.DirectRepositoryWriter](t, r)
+
+	_, err = drw.FormatManager().SetUpgradeLockIntent(testlogging.Context(t), *faultyLock)
 	require.EqualError(t, err, "failed to backup the repo format blob: unable to write format blob \"kopia.repository.backup.faulty-upgrade-owner\": unexpected error")

-	_, err = r.(repo.DirectRepositoryWriter).FormatManager().SetUpgradeLockIntent(testlogging.Context(t), allowedLock)
+	_, err = drw.FormatManager().SetUpgradeLockIntent(testlogging.Context(t), allowedLock)
 	require.NoError(t, err)

-	require.EqualError(t, r.(repo.DirectRepositoryWriter).FormatManager().RollbackUpgrade(testlogging.Context(t)),
+	require.EqualError(t, drw.FormatManager().RollbackUpgrade(testlogging.Context(t)),
 		"failed to delete the format blob backup \"kopia.repository.backup.allowed-upgrade-owner\": unexpected error")

-	require.EqualError(t, r.(repo.DirectRepositoryWriter).FormatManager().RollbackUpgrade(testlogging.Context(t)),
+	require.EqualError(t, drw.FormatManager().RollbackUpgrade(testlogging.Context(t)),
 		"failed to delete the format blob backup \"kopia.repository.backup.allowed-upgrade-owner\": unexpected error")

 	allowPuts = false

-	require.EqualError(t, r.(repo.DirectRepositoryWriter).FormatManager().RollbackUpgrade(testlogging.Context(t)),
+	require.EqualError(t, drw.FormatManager().RollbackUpgrade(testlogging.Context(t)),
 		"failed to restore format blob from backup \"kopia.repository.backup.allowed-upgrade-owner\": unexpected error")

 	allowGets = false

-	require.EqualError(t, r.(repo.DirectRepositoryWriter).FormatManager().RollbackUpgrade(testlogging.Context(t)),
+	require.EqualError(t, drw.FormatManager().RollbackUpgrade(testlogging.Context(t)),
 		"failed to read from backup \"kopia.repository.backup.allowed-upgrade-owner\": unexpected error on get")

 	allowPuts, allowGets, allowDeletes = true, true, true

-	require.NoError(t, r.(repo.DirectRepositoryWriter).FormatManager().RollbackUpgrade(testlogging.Context(t)))
+	require.NoError(t, drw.FormatManager().RollbackUpgrade(testlogging.Context(t)))
 }

 func TestFormatUpgradeDuringOngoingWriteSessions(t *testing.T) {
@@ -330,7 +332,7 @@ func TestFormatUpgradeDuringOngoingWriteSessions(t *testing.T) {

 	rep := env.Repository // read-only

-	lw := rep.(repo.RepositoryWriter)
+	lw := testutil.EnsureType[repo.DirectRepositoryWriter](t, rep)

 	// w1, w2, w3 are independent sessions.
 	_, w1, err := rep.NewWriter(ctx, repo.WriteSessionOptions{Purpose: "writer1"})
@@ -370,7 +372,7 @@ func TestFormatUpgradeDuringOngoingWriteSessions(t *testing.T) {
 	}

 	// set upgrade lock using independent client
-	_, err = env.MustConnectOpenAnother(t).(repo.DirectRepositoryWriter).FormatManager().SetUpgradeLockIntent(ctx, l)
+	_, err = testutil.EnsureType[repo.DirectRepositoryWriter](t, env.MustConnectOpenAnother(t)).FormatManager().SetUpgradeLockIntent(ctx, l)
 	require.NoError(t, err)

 	// ongoing writes should NOT get interrupted because the upgrade lock
@@ -395,7 +397,6 @@ func TestFormatUpgradeDuringOngoingWriteSessions(t *testing.T) {

 	// ongoing writes should get interrupted this time
 	require.ErrorIs(t, w1.Flush(ctx), repo.ErrRepositoryUnavailableDueToUpgradeInProgress)
-
 	require.ErrorIs(t, w2.Flush(ctx), repo.ErrRepositoryUnavailableDueToUpgradeInProgress)
 	require.ErrorIs(t, w3.Flush(ctx), repo.ErrRepositoryUnavailableDueToUpgradeInProgress)
 	require.ErrorIs(t, lw.Flush(ctx), repo.ErrRepositoryUnavailableDueToUpgradeInProgress)
--- a/repo/maintenance/blob_retain_test.go
+++ b/repo/maintenance/blob_retain_test.go
@@ -12,6 +12,7 @@
 	"github.com/kopia/kopia/internal/cache"
 	"github.com/kopia/kopia/internal/faketime"
 	"github.com/kopia/kopia/internal/repotesting"
+	"github.com/kopia/kopia/internal/testutil"
 	"github.com/kopia/kopia/repo"
 	"github.com/kopia/kopia/repo/blob"
 	"github.com/kopia/kopia/repo/encryption"
@@ -56,7 +57,7 @@ func (s *formatSpecificTestSuite) TestExtendBlobRetentionTime(t *testing.T) {
 	require.Len(t, blobsBefore, 4, "unexpected number of blobs after writing")

 	lastBlobIdx := len(blobsBefore) - 1
-	st := env.RootStorage().(blobtesting.RetentionStorage)
+	st := testutil.EnsureType[blobtesting.RetentionStorage](t, env.RootStorage())

 	gotMode, expiry, err := st.GetRetention(ctx, blobsBefore[lastBlobIdx].BlobID)
 	require.NoError(t, err, "getting blob retention info")
@@ -111,7 +112,7 @@ func (s *formatSpecificTestSuite) TestExtendBlobRetentionTimeDisabled(t *testing
 	// Need to continue using TouchBlob because the environment only supports the
 	// locking map if no retention time is given.
 	lastBlobIdx := len(blobsBefore) - 1
-	st := env.RootStorage().(cache.Storage)
+	st := testutil.EnsureType[cache.Storage](t, env.RootStorage())

 	ta.Advance(7 * 24 * time.Hour)

--- a/repo/object/object_manager_test.go
+++ b/repo/object/object_manager_test.go
@@ -498,7 +498,7 @@ func TestIndirection(t *testing.T) {
 		contentBytes := make([]byte, c.dataLength)

 		writer := om.NewWriter(ctx, WriterOptions{MetadataCompressor: c.metadataCompressor})
-		writer.(*objectWriter).splitter = splitterFactory()
+		testutil.EnsureType[*objectWriter](t, writer).splitter = splitterFactory()

 		if _, err := writer.Write(contentBytes); err != nil {
 			t.Errorf("write error: %v", err)
--- a/repo/repository_test.go
+++ b/repo/repository_test.go
@@ -310,7 +310,7 @@ func TestWriterScope(t *testing.T) {

 	rep := env.Repository // read-only

-	lw := rep.(repo.RepositoryWriter)
+	lw := testutil.EnsureType[repo.DirectRepositoryWriter](t, rep)

 	// w1, w2, w3 are independent sessions.
 	_, w1, err := rep.NewWriter(ctx, repo.WriteSessionOptions{Purpose: "writer1"})
@@ -572,7 +572,7 @@ func TestObjectWritesWithRetention(t *testing.T) {

 	var prefixesWithRetention []string

-	versionedMap := env.RootStorage().(cache.Storage)
+	versionedMap := testutil.EnsureType[cache.Storage](t, env.RootStorage())

 	for _, prefix := range content.PackBlobIDPrefixes {
 		prefixesWithRetention = append(prefixesWithRetention, string(prefix))
@@ -891,7 +891,7 @@ func TestDeriveKey(t *testing.T) {
 		})

 		// prepare upgrade
-		dw1Upgraded := env.Repository.(repo.DirectRepositoryWriter)
+		dw1Upgraded := testutil.EnsureType[repo.DirectRepositoryWriter](t, env.Repository)
 		cf := dw1Upgraded.ContentReader().ContentFormat()

 		mp, mperr := cf.GetMutableParameters(ctx)
@@ -908,7 +908,7 @@ func TestDeriveKey(t *testing.T) {

 		require.NoError(t, dw1Upgraded.FormatManager().SetParameters(ctx, mp, blobCfg, feat))

-		return env.MustConnectOpenAnother(t).(repo.DirectRepositoryWriter)
+		return testutil.EnsureType[repo.DirectRepositoryWriter](t, env.MustConnectOpenAnother(t))
 	}

 	// we verify that repositories started on V1 will continue to derive keys from
--- a/snapshot/snapshotfs/source_directories_test.go
+++ b/snapshot/snapshotfs/source_directories_test.go
@@ -2,6 +2,7 @@

 import (
 	"context"
+	"maps"
 	"testing"
 	"time"

@@ -10,6 +11,7 @@
 	"github.com/kopia/kopia/fs"
 	"github.com/kopia/kopia/internal/mockfs"
 	"github.com/kopia/kopia/internal/repotesting"
+	"github.com/kopia/kopia/internal/testutil"
 	"github.com/kopia/kopia/repo"
 	"github.com/kopia/kopia/snapshot"
 	"github.com/kopia/kopia/snapshot/snapshotfs"
@@ -87,11 +89,10 @@ func iterateAllNames(ctx context.Context, t *testing.T, dir fs.Directory, prefix
 	err := fs.IterateEntries(ctx, dir, func(innerCtx context.Context, ent fs.Entry) error {
 		if ent.IsDir() {
 			result[prefix+ent.Name()+"/"] = struct{}{}
-			childEntries := iterateAllNames(ctx, t, ent.(fs.Directory), prefix+ent.Name()+"/")

-			for k, v := range childEntries {
-				result[k] = v
-			}
+			childEntries := iterateAllNames(ctx, t, testutil.EnsureType[fs.Directory](t, ent), prefix+ent.Name()+"/")
+
+			maps.Copy(result, childEntries)
 		} else {
 			result[prefix+ent.Name()] = struct{}{}
 		}
--- a/snapshot/snapshotmaintenance/snapshotmaintenance_test.go
+++ b/snapshot/snapshotmaintenance/snapshotmaintenance_test.go
@@ -15,6 +15,7 @@
 	"github.com/kopia/kopia/internal/mockfs"
 	"github.com/kopia/kopia/internal/repotesting"
 	"github.com/kopia/kopia/internal/testlogging"
+	"github.com/kopia/kopia/internal/testutil"
 	"github.com/kopia/kopia/repo"
 	"github.com/kopia/kopia/repo/content"
 	"github.com/kopia/kopia/repo/format"
@@ -132,7 +133,7 @@ func (s *formatSpecificTestSuite) TestMaintenanceReuseDirManifest(t *testing.T)
 	err = snapshotmaintenance.Run(ctx, th.RepositoryWriter, maintenance.ModeFull, true, maintenance.SafetyFull)
 	require.NoError(t, err)

-	info, err := r2.(repo.DirectRepository).ContentInfo(ctx, mustGetContentID(t, s2.RootObjectID()))
+	info, err := testutil.EnsureType[repo.DirectRepository](t, r2).ContentInfo(ctx, mustGetContentID(t, s2.RootObjectID()))
 	require.NoError(t, err)
 	require.False(t, info.Deleted, "content must not be deleted")

--- a/snapshot/upload/upload_test.go
+++ b/snapshot/upload/upload_test.go
@@ -203,7 +203,7 @@ func findAllEntries(t *testing.T, ctx context.Context, dir fs.Directory) []entry
 	entries := []entry{}

 	fs.IterateEntries(ctx, dir, func(ctx context.Context, e fs.Entry) error {
-		oid, err := object.ParseID(e.(object.HasObjectID).ObjectID().String())
+		oid, err := object.ParseID(testutil.EnsureType[object.HasObjectID](t, e).ObjectID().String())
 		require.NoError(t, err)

 		entries = append(entries, entry{
@@ -211,7 +211,7 @@ func findAllEntries(t *testing.T, ctx context.Context, dir fs.Directory) []entry
 			objectID: oid,
 		})
 		if e.IsDir() {
-			entries = append(entries, findAllEntries(t, ctx, e.(fs.Directory))...)
+			entries = append(entries, findAllEntries(t, ctx, testutil.EnsureType[fs.Directory](t, e))...)
 		}

 		return nil
@@ -290,7 +290,7 @@ func TestUploadMetadataCompression(t *testing.T) {
 			s1, err := u.Upload(ctx, th.sourceDir, policyTree, snapshot.SourceInfo{})
 			require.NoError(t, err, "upload error")

-			dir := snapshotfs.EntryFromDirEntry(th.repo, s1.RootEntry).(fs.Directory)
+			dir := testutil.EnsureType[fs.Directory](t, snapshotfs.EntryFromDirEntry(th.repo, s1.RootEntry))
 			entries := findAllEntries(t, ctx, dir)
 			verifyMetadataCompressor(t, ctx, th.repo, entries, compID)
 		})
@@ -1253,21 +1253,19 @@ func TestParallelUploadOfLargeFiles(t *testing.T) {

 	t.Logf("man: %v", man.RootObjectID())

-	dir := snapshotfs.EntryFromDirEntry(th.repo, man.RootEntry).(fs.Directory)
-
+	dir := testutil.EnsureType[fs.Directory](t, snapshotfs.EntryFromDirEntry(th.repo, man.RootEntry))
 	successCount := 0

 	fs.IterateEntries(ctx, dir, func(ctx context.Context, e fs.Entry) error {
 		if f, ok := e.(fs.File); ok {
-			hoid, hasObjectId := f.(object.HasObjectID)
-			require.True(t, hasObjectId)
+			hoid := testutil.EnsureType[object.HasObjectID](t, f)

 			oids := hoid.ObjectID().String()

 			oid, err := object.ParseID(strings.TrimPrefix(oids, "I"))
 			require.NoError(t, err, "failed to parse object id", oids)

-			entries, err := object.LoadIndexObject(ctx, th.repo.(repo.DirectRepositoryWriter).ContentManager(), oid)
+			entries, err := object.LoadIndexObject(ctx, testutil.EnsureType[repo.DirectRepositoryWriter](t, th.repo).ContentManager(), oid)
 			require.NoError(t, err, "failed to parse indirect object id", oid)

 			// ensure that index object contains breakpoints at all multiples of 'chunkSize'.
--- a/tests/endurance_test/endurance_test.go
+++ b/tests/endurance_test/endurance_test.go
@@ -50,7 +50,7 @@ func (d webdavDirWithFakeClock) OpenFile(ctx context.Context, fname string, flag
 	}

 	// change file time after creation to simulate fake time scale.
-	osf := f.(*os.File)
+	osf := f.(*os.File) //nolint:forcetypeassert
 	now := d.fts.Now()

 	if err := os.Chtimes(osf.Name(), now, now); err != nil {
--- a/tests/repository_stress_test/repository_stress_test.go
+++ b/tests/repository_stress_test/repository_stress_test.go
@@ -303,7 +303,7 @@ func longLivedRepositoryTest(ctx context.Context, t *testing.T, openID, configFi
 	for i := range opt.SessionsPerOpenRepository {
 		ors := or.NewSession(fmt.Sprintf("session-%v", i))

-		_, w, err := rep.(repo.DirectRepository).NewDirectWriter(ctx, repo.WriteSessionOptions{
+		_, w, err := testutil.EnsureType[repo.DirectRepository](t, rep).NewDirectWriter(ctx, repo.WriteSessionOptions{
 			Purpose: fmt.Sprintf("longLivedRepositoryTest-w%v", i),
 		})
 		if err != nil {
--- a/tests/socketactivation_test/socketactivation_test.go
+++ b/tests/socketactivation_test/socketactivation_test.go
@@ -43,7 +43,7 @@ func TestServerControlSocketActivated(t *testing.T) {
 		l1.Close()
 	}()

-	port = l1.Addr().(*net.TCPAddr).Port
+	port = testutil.EnsureType[*net.TCPAddr](t, l1.Addr()).Port

 	t.Logf("Activating socket on port %v", port)

@@ -53,7 +53,7 @@ func TestServerControlSocketActivated(t *testing.T) {
 	var sp testutil.ServerParameters

 	go func() {
-		l1File, err := l1.(*net.TCPListener).File()
+		l1File, err := testutil.EnsureType[*net.TCPListener](t, l1).File()
 		if err != nil {
 			t.Log("ERROR: Failed to get filehandle for socket")
 			close(serverStarted)
@@ -121,14 +121,16 @@ func TestServerControlSocketActivatedTooManyFDs(t *testing.T) {
 		l1.Close()
 	}()

-	port = l1.Addr().(*net.TCPAddr).Port
+	port = testutil.EnsureType[*net.TCPAddr](t, l1.Addr()).Port

 	t.Logf("Activating socket on port %v", port)

 	serverStarted := make(chan []string)

 	go func() {
-		l1File, err := l1.(*net.TCPListener).File()
+		listener := testutil.EnsureType[*net.TCPListener](t, l1)
+
+		l1File, err := listener.File()
 		if err != nil {
 			t.Log("Failed to get filehandle for socket")
 			close(serverStarted)
@@ -136,7 +138,7 @@ func TestServerControlSocketActivatedTooManyFDs(t *testing.T) {
 			return
 		}

-		l2File, err := l1.(*net.TCPListener).File()
+		l2File, err := listener.File()
 		if err != nil {
 			t.Log("Failed to get 2nd filehandle for socket")
 			close(serverStarted)