diff --git a/internal/backend/azure/azure_test.go b/internal/backend/azure/azure_test.go
index 4e33e8a39..f7492ae1b 100644
--- a/internal/backend/azure/azure_test.go
+++ b/internal/backend/azure/azure_test.go
@@ -18,21 +18,21 @@ import (
 	rtest "github.com/restic/restic/internal/test"
 )
 
-func newAzureTestSuite(t testing.TB) *test.Suite {
+func newAzureTestSuite(t testing.TB) *test.Suite[azure.Config] {
 	tr, err := backend.Transport(backend.TransportOptions{})
 	if err != nil {
 		t.Fatalf("cannot create transport for tests: %v", err)
 	}
 
-	return &test.Suite{
+	return &test.Suite[azure.Config]{
 		// do not use excessive data
 		MinimalData: true,
 
 		// NewConfig returns a config for a new temporary backend that will be used in tests.
-		NewConfig: func() (interface{}, error) {
+		NewConfig: func() (azure.Config, error) {
 			cfg, err := azure.ParseConfig(os.Getenv("RESTIC_TEST_AZURE_REPOSITORY"))
 			if err != nil {
-				return nil, err
+				return azure.Config{}, err
 			}
 
 			cfg.AccountName = os.Getenv("RESTIC_TEST_AZURE_ACCOUNT_NAME")
@@ -42,9 +42,7 @@ func newAzureTestSuite(t testing.TB) *test.Suite {
 		},
 
 		// CreateFn is a function that creates a temporary repository for the tests.
-		Create: func(config interface{}) (restic.Backend, error) {
-			cfg := config.(azure.Config)
-
+		Create: func(cfg azure.Config) (restic.Backend, error) {
 			ctx := context.TODO()
 			be, err := azure.Create(ctx, cfg, tr)
 			if err != nil {
@@ -64,15 +62,13 @@ func newAzureTestSuite(t testing.TB) *test.Suite {
 		},
 
 		// OpenFn is a function that opens a previously created temporary repository.
-		Open: func(config interface{}) (restic.Backend, error) {
-			cfg := config.(azure.Config)
+		Open: func(cfg azure.Config) (restic.Backend, error) {
 			ctx := context.TODO()
 			return azure.Open(ctx, cfg, tr)
 		},
 
 		// CleanupFn removes data created during the tests.
-		Cleanup: func(config interface{}) error {
-			cfg := config.(azure.Config)
+		Cleanup: func(cfg azure.Config) error {
 			ctx := context.TODO()
 			be, err := azure.Open(ctx, cfg, tr)
 			if err != nil {
diff --git a/internal/backend/b2/b2_test.go b/internal/backend/b2/b2_test.go
index d7112410a..f634852d0 100644
--- a/internal/backend/b2/b2_test.go
+++ b/internal/backend/b2/b2_test.go
@@ -16,13 +16,13 @@ import (
 	rtest "github.com/restic/restic/internal/test"
 )
 
-func newB2TestSuite(t testing.TB) *test.Suite {
+func newB2TestSuite(t testing.TB) *test.Suite[b2.Config] {
 	tr, err := backend.Transport(backend.TransportOptions{})
 	if err != nil {
 		t.Fatalf("cannot create transport for tests: %v", err)
 	}
 
-	return &test.Suite{
+	return &test.Suite[b2.Config]{
 		// do not use excessive data
 		MinimalData: true,
 
@@ -30,10 +30,10 @@ func newB2TestSuite(t testing.TB) *test.Suite {
 		WaitForDelayedRemoval: 10 * time.Second,
 
 		// NewConfig returns a config for a new temporary backend that will be used in tests.
-		NewConfig: func() (interface{}, error) {
+		NewConfig: func() (b2.Config, error) {
 			cfg, err := b2.ParseConfig(os.Getenv("RESTIC_TEST_B2_REPOSITORY"))
 			if err != nil {
-				return nil, err
+				return b2.Config{}, err
 			}
 
 			cfg.AccountID = os.Getenv("RESTIC_TEST_B2_ACCOUNT_ID")
@@ -43,20 +43,17 @@ func newB2TestSuite(t testing.TB) *test.Suite {
 		},
 
 		// CreateFn is a function that creates a temporary repository for the tests.
-		Create: func(config interface{}) (restic.Backend, error) {
-			cfg := config.(b2.Config)
+		Create: func(cfg b2.Config) (restic.Backend, error) {
 			return b2.Create(context.Background(), cfg, tr)
 		},
 
 		// OpenFn is a function that opens a previously created temporary repository.
-		Open: func(config interface{}) (restic.Backend, error) {
-			cfg := config.(b2.Config)
+		Open: func(cfg b2.Config) (restic.Backend, error) {
 			return b2.Open(context.Background(), cfg, tr)
 		},
 
 		// CleanupFn removes data created during the tests.
-		Cleanup: func(config interface{}) error {
-			cfg := config.(b2.Config)
+		Cleanup: func(cfg b2.Config) error {
 			be, err := b2.Open(context.Background(), cfg, tr)
 			if err != nil {
 				return err
diff --git a/internal/backend/gs/gs_test.go b/internal/backend/gs/gs_test.go
index 20b51e5cc..b9015e24c 100644
--- a/internal/backend/gs/gs_test.go
+++ b/internal/backend/gs/gs_test.go
@@ -15,21 +15,21 @@ import (
 	rtest "github.com/restic/restic/internal/test"
 )
 
-func newGSTestSuite(t testing.TB) *test.Suite {
+func newGSTestSuite(t testing.TB) *test.Suite[gs.Config] {
 	tr, err := backend.Transport(backend.TransportOptions{})
 	if err != nil {
 		t.Fatalf("cannot create transport for tests: %v", err)
 	}
 
-	return &test.Suite{
+	return &test.Suite[gs.Config]{
 		// do not use excessive data
 		MinimalData: true,
 
 		// NewConfig returns a config for a new temporary backend that will be used in tests.
-		NewConfig: func() (interface{}, error) {
+		NewConfig: func() (gs.Config, error) {
 			cfg, err := gs.ParseConfig(os.Getenv("RESTIC_TEST_GS_REPOSITORY"))
 			if err != nil {
-				return nil, err
+				return gs.Config{}, err
 			}
 
 			cfg.ProjectID = os.Getenv("RESTIC_TEST_GS_PROJECT_ID")
@@ -38,9 +38,7 @@ func newGSTestSuite(t testing.TB) *test.Suite {
 		},
 
 		// CreateFn is a function that creates a temporary repository for the tests.
-		Create: func(config interface{}) (restic.Backend, error) {
-			cfg := config.(gs.Config)
-
+		Create: func(cfg gs.Config) (restic.Backend, error) {
 			be, err := gs.Create(context.Background(), cfg, tr)
 			if err != nil {
 				return nil, err
@@ -59,15 +57,12 @@ func newGSTestSuite(t testing.TB) *test.Suite {
 		},
 
 		// OpenFn is a function that opens a previously created temporary repository.
-		Open: func(config interface{}) (restic.Backend, error) {
-			cfg := config.(gs.Config)
+		Open: func(cfg gs.Config) (restic.Backend, error) {
 			return gs.Open(cfg, tr)
 		},
 
 		// CleanupFn removes data created during the tests.
-		Cleanup: func(config interface{}) error {
-			cfg := config.(gs.Config)
-
+		Cleanup: func(cfg gs.Config) error {
 			be, err := gs.Open(cfg, tr)
 			if err != nil {
 				return err
diff --git a/internal/backend/local/local_test.go b/internal/backend/local/local_test.go
index 495f220a0..98afc5963 100644
--- a/internal/backend/local/local_test.go
+++ b/internal/backend/local/local_test.go
@@ -12,10 +12,10 @@ import (
 	rtest "github.com/restic/restic/internal/test"
 )
 
-func newTestSuite(t testing.TB) *test.Suite {
-	return &test.Suite{
+func newTestSuite(t testing.TB) *test.Suite[local.Config] {
+	return &test.Suite[local.Config]{
 		// NewConfig returns a config for a new temporary backend that will be used in tests.
-		NewConfig: func() (interface{}, error) {
+		NewConfig: func() (local.Config, error) {
 			dir, err := os.MkdirTemp(rtest.TestTempDir, "restic-test-local-")
 			if err != nil {
 				t.Fatal(err)
@@ -31,20 +31,17 @@ func newTestSuite(t testing.TB) *test.Suite {
 		},
 
 		// CreateFn is a function that creates a temporary repository for the tests.
-		Create: func(config interface{}) (restic.Backend, error) {
-			cfg := config.(local.Config)
+		Create: func(cfg local.Config) (restic.Backend, error) {
 			return local.Create(context.TODO(), cfg)
 		},
 
 		// OpenFn is a function that opens a previously created temporary repository.
-		Open: func(config interface{}) (restic.Backend, error) {
-			cfg := config.(local.Config)
+		Open: func(cfg local.Config) (restic.Backend, error) {
 			return local.Open(context.TODO(), cfg)
 		},
 
 		// CleanupFn removes data created during the tests.
-		Cleanup: func(config interface{}) error {
-			cfg := config.(local.Config)
+		Cleanup: func(cfg local.Config) error {
 			if !rtest.TestCleanupTempDirs {
 				t.Logf("leaving test backend dir at %v", cfg.Path)
 			}
diff --git a/internal/backend/mem/mem_backend_test.go b/internal/backend/mem/mem_backend_test.go
index 819c6a2b6..7b862e314 100644
--- a/internal/backend/mem/mem_backend_test.go
+++ b/internal/backend/mem/mem_backend_test.go
@@ -15,19 +15,18 @@ type memConfig struct {
 	be restic.Backend
 }
 
-func newTestSuite() *test.Suite {
-	return &test.Suite{
+func newTestSuite() *test.Suite[*memConfig] {
+	return &test.Suite[*memConfig]{
 		// NewConfig returns a config for a new temporary backend that will be used in tests.
-		NewConfig: func() (interface{}, error) {
+		NewConfig: func() (*memConfig, error) {
 			return &memConfig{}, nil
 		},
 
 		// CreateFn is a function that creates a temporary repository for the tests.
-		Create: func(cfg interface{}) (restic.Backend, error) {
-			c := cfg.(*memConfig)
-			if c.be != nil {
-				_, err := c.be.Stat(context.TODO(), restic.Handle{Type: restic.ConfigFile})
-				if err != nil && !c.be.IsNotExist(err) {
+		Create: func(cfg *memConfig) (restic.Backend, error) {
+			if cfg.be != nil {
+				_, err := cfg.be.Stat(context.TODO(), restic.Handle{Type: restic.ConfigFile})
+				if err != nil && !cfg.be.IsNotExist(err) {
 					return nil, err
 				}
 
@@ -36,21 +35,20 @@ func newTestSuite() *test.Suite {
 				}
 			}
 
-			c.be = mem.New()
-			return c.be, nil
+			cfg.be = mem.New()
+			return cfg.be, nil
 		},
 
 		// OpenFn is a function that opens a previously created temporary repository.
-		Open: func(cfg interface{}) (restic.Backend, error) {
-			c := cfg.(*memConfig)
-			if c.be == nil {
-				c.be = mem.New()
+		Open: func(cfg *memConfig) (restic.Backend, error) {
+			if cfg.be == nil {
+				cfg.be = mem.New()
 			}
-			return c.be, nil
+			return cfg.be, nil
 		},
 
 		// CleanupFn removes data created during the tests.
-		Cleanup: func(cfg interface{}) error {
+		Cleanup: func(cfg *memConfig) error {
 			// no cleanup needed
 			return nil
 		},
diff --git a/internal/backend/rclone/backend_test.go b/internal/backend/rclone/backend_test.go
index 12fed6274..4bff46d77 100644
--- a/internal/backend/rclone/backend_test.go
+++ b/internal/backend/rclone/backend_test.go
@@ -12,12 +12,12 @@ import (
 	rtest "github.com/restic/restic/internal/test"
 )
 
-func newTestSuite(t testing.TB) *test.Suite {
+func newTestSuite(t testing.TB) *test.Suite[rclone.Config] {
 	dir := rtest.TempDir(t)
 
-	return &test.Suite{
+	return &test.Suite[rclone.Config]{
 		// NewConfig returns a config for a new temporary backend that will be used in tests.
-		NewConfig: func() (interface{}, error) {
+		NewConfig: func() (rclone.Config, error) {
 			t.Logf("use backend at %v", dir)
 			cfg := rclone.NewConfig()
 			cfg.Remote = dir
@@ -25,9 +25,8 @@ func newTestSuite(t testing.TB) *test.Suite {
 		},
 
 		// CreateFn is a function that creates a temporary repository for the tests.
-		Create: func(config interface{}) (restic.Backend, error) {
+		Create: func(cfg rclone.Config) (restic.Backend, error) {
 			t.Logf("Create()")
-			cfg := config.(rclone.Config)
 			be, err := rclone.Create(context.TODO(), cfg)
 			var e *exec.Error
 			if errors.As(err, &e) && e.Err == exec.ErrNotFound {
@@ -38,9 +37,8 @@ func newTestSuite(t testing.TB) *test.Suite {
 		},
 
 		// OpenFn is a function that opens a previously created temporary repository.
-		Open: func(config interface{}) (restic.Backend, error) {
+		Open: func(cfg rclone.Config) (restic.Backend, error) {
 			t.Logf("Open()")
-			cfg := config.(rclone.Config)
 			return rclone.Open(cfg, nil)
 		},
 	}
diff --git a/internal/backend/rest/rest_test.go b/internal/backend/rest/rest_test.go
index edbb3141c..10e7b5b5b 100644
--- a/internal/backend/rest/rest_test.go
+++ b/internal/backend/rest/rest_test.go
@@ -67,36 +67,34 @@ func runRESTServer(ctx context.Context, t testing.TB, dir string) (*url.URL, fun
 	return url, cleanup
 }
 
-func newTestSuite(_ context.Context, t testing.TB, url *url.URL, minimalData bool) *test.Suite {
+func newTestSuite(_ context.Context, t testing.TB, url *url.URL, minimalData bool) *test.Suite[rest.Config] {
 	tr, err := backend.Transport(backend.TransportOptions{})
 	if err != nil {
 		t.Fatalf("cannot create transport for tests: %v", err)
 	}
 
-	return &test.Suite{
+	return &test.Suite[rest.Config]{
 		MinimalData: minimalData,
 
 		// NewConfig returns a config for a new temporary backend that will be used in tests.
-		NewConfig: func() (interface{}, error) {
+		NewConfig: func() (rest.Config, error) {
 			cfg := rest.NewConfig()
 			cfg.URL = url
 			return cfg, nil
 		},
 
 		// CreateFn is a function that creates a temporary repository for the tests.
-		Create: func(config interface{}) (restic.Backend, error) {
-			cfg := config.(rest.Config)
+		Create: func(cfg rest.Config) (restic.Backend, error) {
 			return rest.Create(context.TODO(), cfg, tr)
 		},
 
 		// OpenFn is a function that opens a previously created temporary repository.
-		Open: func(config interface{}) (restic.Backend, error) {
-			cfg := config.(rest.Config)
+		Open: func(cfg rest.Config) (restic.Backend, error) {
 			return rest.Open(cfg, tr)
 		},
 
 		// CleanupFn removes data created during the tests.
-		Cleanup: func(config interface{}) error {
+		Cleanup: func(cfg rest.Config) error {
 			return nil
 		},
 	}
diff --git a/internal/backend/s3/s3_test.go b/internal/backend/s3/s3_test.go
index 6df81232a..5c91e9f7f 100644
--- a/internal/backend/s3/s3_test.go
+++ b/internal/backend/s3/s3_test.go
@@ -120,15 +120,15 @@ func createS3(t testing.TB, cfg MinioTestConfig, tr http.RoundTripper) (be resti
 	return be, err
 }
 
-func newMinioTestSuite(ctx context.Context, t testing.TB) *test.Suite {
+func newMinioTestSuite(ctx context.Context, t testing.TB) *test.Suite[MinioTestConfig] {
 	tr, err := backend.Transport(backend.TransportOptions{})
 	if err != nil {
 		t.Fatalf("cannot create transport for tests: %v", err)
 	}
 
-	return &test.Suite{
+	return &test.Suite[MinioTestConfig]{
 		// NewConfig returns a config for a new temporary backend that will be used in tests.
-		NewConfig: func() (interface{}, error) {
+		NewConfig: func() (MinioTestConfig, error) {
 			cfg := MinioTestConfig{}
 
 			cfg.tempdir = rtest.TempDir(t)
@@ -146,9 +146,7 @@ func newMinioTestSuite(ctx context.Context, t testing.TB) *test.Suite {
 		},
 
 		// CreateFn is a function that creates a temporary repository for the tests.
-		Create: func(config interface{}) (restic.Backend, error) {
-			cfg := config.(MinioTestConfig)
-
+		Create: func(cfg MinioTestConfig) (restic.Backend, error) {
 			be, err := createS3(t, cfg, tr)
 			if err != nil {
 				return nil, err
@@ -167,14 +165,12 @@ func newMinioTestSuite(ctx context.Context, t testing.TB) *test.Suite {
 		},
 
 		// OpenFn is a function that opens a previously created temporary repository.
-		Open: func(config interface{}) (restic.Backend, error) {
-			cfg := config.(MinioTestConfig)
+		Open: func(cfg MinioTestConfig) (restic.Backend, error) {
 			return s3.Open(ctx, cfg.Config, tr)
 		},
 
 		// CleanupFn removes data created during the tests.
-		Cleanup: func(config interface{}) error {
-			cfg := config.(MinioTestConfig)
+		Cleanup: func(cfg MinioTestConfig) error {
 			if cfg.stopServer != nil {
 				cfg.stopServer()
 			}
@@ -217,21 +213,21 @@ func BenchmarkBackendMinio(t *testing.B) {
 	newMinioTestSuite(ctx, t).RunBenchmarks(t)
 }
 
-func newS3TestSuite(t testing.TB) *test.Suite {
+func newS3TestSuite(t testing.TB) *test.Suite[s3.Config] {
 	tr, err := backend.Transport(backend.TransportOptions{})
 	if err != nil {
 		t.Fatalf("cannot create transport for tests: %v", err)
 	}
 
-	return &test.Suite{
+	return &test.Suite[s3.Config]{
 		// do not use excessive data
 		MinimalData: true,
 
 		// NewConfig returns a config for a new temporary backend that will be used in tests.
-		NewConfig: func() (interface{}, error) {
+		NewConfig: func() (s3.Config, error) {
 			cfg, err := s3.ParseConfig(os.Getenv("RESTIC_TEST_S3_REPOSITORY"))
 			if err != nil {
-				return nil, err
+				return s3.Config{}, err
 			}
 
 			cfg.KeyID = os.Getenv("RESTIC_TEST_S3_KEY")
@@ -241,9 +237,7 @@ func newS3TestSuite(t testing.TB) *test.Suite {
 		},
 
 		// CreateFn is a function that creates a temporary repository for the tests.
-		Create: func(config interface{}) (restic.Backend, error) {
-			cfg := config.(s3.Config)
-
+		Create: func(cfg s3.Config) (restic.Backend, error) {
 			be, err := s3.Create(context.TODO(), cfg, tr)
 			if err != nil {
 				return nil, err
@@ -262,15 +256,12 @@ func newS3TestSuite(t testing.TB) *test.Suite {
 		},
 
 		// OpenFn is a function that opens a previously created temporary repository.
-		Open: func(config interface{}) (restic.Backend, error) {
-			cfg := config.(s3.Config)
+		Open: func(cfg s3.Config) (restic.Backend, error) {
 			return s3.Open(context.TODO(), cfg, tr)
 		},
 
 		// CleanupFn removes data created during the tests.
-		Cleanup: func(config interface{}) error {
-			cfg := config.(s3.Config)
-
+		Cleanup: func(cfg s3.Config) error {
 			be, err := s3.Open(context.TODO(), cfg, tr)
 			if err != nil {
 				return err
diff --git a/internal/backend/sftp/sftp_test.go b/internal/backend/sftp/sftp_test.go
index 0dbcd291c..34ad06554 100644
--- a/internal/backend/sftp/sftp_test.go
+++ b/internal/backend/sftp/sftp_test.go
@@ -29,10 +29,10 @@ func findSFTPServerBinary() string {
 
 var sftpServer = findSFTPServerBinary()
 
-func newTestSuite(t testing.TB) *test.Suite {
-	return &test.Suite{
+func newTestSuite(t testing.TB) *test.Suite[sftp.Config] {
+	return &test.Suite[sftp.Config]{
 		// NewConfig returns a config for a new temporary backend that will be used in tests.
-		NewConfig: func() (interface{}, error) {
+		NewConfig: func() (sftp.Config, error) {
 			dir, err := os.MkdirTemp(rtest.TestTempDir, "restic-test-sftp-")
 			if err != nil {
 				t.Fatal(err)
@@ -49,20 +49,17 @@ func newTestSuite(t testing.TB) *test.Suite {
 		},
 
 		// CreateFn is a function that creates a temporary repository for the tests.
-		Create: func(config interface{}) (restic.Backend, error) {
-			cfg := config.(sftp.Config)
+		Create: func(cfg sftp.Config) (restic.Backend, error) {
 			return sftp.Create(context.TODO(), cfg)
 		},
 
 		// OpenFn is a function that opens a previously created temporary repository.
-		Open: func(config interface{}) (restic.Backend, error) {
-			cfg := config.(sftp.Config)
+		Open: func(cfg sftp.Config) (restic.Backend, error) {
 			return sftp.Open(context.TODO(), cfg)
 		},
 
 		// CleanupFn removes data created during the tests.
-		Cleanup: func(config interface{}) error {
-			cfg := config.(sftp.Config)
+		Cleanup: func(cfg sftp.Config) error {
 			if !rtest.TestCleanupTempDirs {
 				t.Logf("leaving test backend dir at %v", cfg.Path)
 			}
diff --git a/internal/backend/swift/swift_test.go b/internal/backend/swift/swift_test.go
index 18c8db93c..316028b0c 100644
--- a/internal/backend/swift/swift_test.go
+++ b/internal/backend/swift/swift_test.go
@@ -15,13 +15,13 @@ import (
 	rtest "github.com/restic/restic/internal/test"
 )
 
-func newSwiftTestSuite(t testing.TB) *test.Suite {
+func newSwiftTestSuite(t testing.TB) *test.Suite[swift.Config] {
 	tr, err := backend.Transport(backend.TransportOptions{})
 	if err != nil {
 		t.Fatalf("cannot create transport for tests: %v", err)
 	}
 
-	return &test.Suite{
+	return &test.Suite[swift.Config]{
 		// do not use excessive data
 		MinimalData: true,
 
@@ -42,14 +42,14 @@ func newSwiftTestSuite(t testing.TB) *test.Suite {
 		},
 
 		// NewConfig returns a config for a new temporary backend that will be used in tests.
-		NewConfig: func() (interface{}, error) {
+		NewConfig: func() (swift.Config, error) {
 			cfg, err := swift.ParseConfig(os.Getenv("RESTIC_TEST_SWIFT"))
 			if err != nil {
-				return nil, err
+				return swift.Config{}, err
 			}
 
 			if err = swift.ApplyEnvironment("RESTIC_TEST_", &cfg); err != nil {
-				return nil, err
+				return swift.Config{}, err
 			}
 			cfg.Prefix += fmt.Sprintf("/test-%d", time.Now().UnixNano())
 			t.Logf("using prefix %v", cfg.Prefix)
@@ -57,9 +57,7 @@ func newSwiftTestSuite(t testing.TB) *test.Suite {
 		},
 
 		// CreateFn is a function that creates a temporary repository for the tests.
-		Create: func(config interface{}) (restic.Backend, error) {
-			cfg := config.(swift.Config)
-
+		Create: func(cfg swift.Config) (restic.Backend, error) {
 			be, err := swift.Open(context.TODO(), cfg, tr)
 			if err != nil {
 				return nil, err
@@ -78,15 +76,12 @@ func newSwiftTestSuite(t testing.TB) *test.Suite {
 		},
 
 		// OpenFn is a function that opens a previously created temporary repository.
-		Open: func(config interface{}) (restic.Backend, error) {
-			cfg := config.(swift.Config)
+		Open: func(cfg swift.Config) (restic.Backend, error) {
 			return swift.Open(context.TODO(), cfg, tr)
 		},
 
 		// CleanupFn removes data created during the tests.
-		Cleanup: func(config interface{}) error {
-			cfg := config.(swift.Config)
-
+		Cleanup: func(cfg swift.Config) error {
 			be, err := swift.Open(context.TODO(), cfg, tr)
 			if err != nil {
 				return err
diff --git a/internal/backend/test/benchmarks.go b/internal/backend/test/benchmarks.go
index b977eb682..150ef3987 100644
--- a/internal/backend/test/benchmarks.go
+++ b/internal/backend/test/benchmarks.go
@@ -29,7 +29,7 @@ func remove(t testing.TB, be restic.Backend, h restic.Handle) {
 
 // BenchmarkLoadFile benchmarks the Load() method of a backend by
 // loading a complete file.
-func (s *Suite) BenchmarkLoadFile(t *testing.B) {
+func (s *Suite[C]) BenchmarkLoadFile(t *testing.B) {
 	be := s.open(t)
 	defer s.close(t, be)
 
@@ -64,7 +64,7 @@ func (s *Suite) BenchmarkLoadFile(t *testing.B) {
 
 // BenchmarkLoadPartialFile benchmarks the Load() method of a backend by
 // loading the remainder of a file starting at a given offset.
-func (s *Suite) BenchmarkLoadPartialFile(t *testing.B) {
+func (s *Suite[C]) BenchmarkLoadPartialFile(t *testing.B) {
 	be := s.open(t)
 	defer s.close(t, be)
 
@@ -101,7 +101,7 @@ func (s *Suite) BenchmarkLoadPartialFile(t *testing.B) {
 
 // BenchmarkLoadPartialFileOffset benchmarks the Load() method of a
 // backend by loading a number of bytes of a file starting at a given offset.
-func (s *Suite) BenchmarkLoadPartialFileOffset(t *testing.B) {
+func (s *Suite[C]) BenchmarkLoadPartialFileOffset(t *testing.B) {
 	be := s.open(t)
 	defer s.close(t, be)
 
@@ -139,7 +139,7 @@ func (s *Suite) BenchmarkLoadPartialFileOffset(t *testing.B) {
 }
 
 // BenchmarkSave benchmarks the Save() method of a backend.
-func (s *Suite) BenchmarkSave(t *testing.B) {
+func (s *Suite[C]) BenchmarkSave(t *testing.B) {
 	be := s.open(t)
 	defer s.close(t, be)
 
diff --git a/internal/backend/test/suite.go b/internal/backend/test/suite.go
index 45c6d96bd..fcb1b00b4 100644
--- a/internal/backend/test/suite.go
+++ b/internal/backend/test/suite.go
@@ -11,21 +11,21 @@ import (
 )
 
 // Suite implements a test suite for restic backends.
-type Suite struct {
+type Suite[C any] struct {
 	// Config should be used to configure the backend.
-	Config interface{}
+	Config C
 
 	// NewConfig returns a config for a new temporary backend that will be used in tests.
-	NewConfig func() (interface{}, error)
+	NewConfig func() (C, error)
 
 	// CreateFn is a function that creates a temporary repository for the tests.
-	Create func(cfg interface{}) (restic.Backend, error)
+	Create func(cfg C) (restic.Backend, error)
 
 	// OpenFn is a function that opens a previously created temporary repository.
-	Open func(cfg interface{}) (restic.Backend, error)
+	Open func(cfg C) (restic.Backend, error)
 
 	// CleanupFn removes data created during the tests.
-	Cleanup func(cfg interface{}) error
+	Cleanup func(cfg C) error
 
 	// MinimalData instructs the tests to not use excessive data.
 	MinimalData bool
@@ -40,7 +40,7 @@ type Suite struct {
 }
 
 // RunTests executes all defined tests as subtests of t.
-func (s *Suite) RunTests(t *testing.T) {
+func (s *Suite[C]) RunTests(t *testing.T) {
 	var err error
 	s.Config, err = s.NewConfig()
 	if err != nil {
@@ -72,7 +72,7 @@ type testFunction struct {
 	Fn   func(*testing.T)
 }
 
-func (s *Suite) testFuncs(t testing.TB) (funcs []testFunction) {
+func (s *Suite[C]) testFuncs(t testing.TB) (funcs []testFunction) {
 	tpe := reflect.TypeOf(s)
 	v := reflect.ValueOf(s)
 
@@ -107,7 +107,7 @@ type benchmarkFunction struct {
 	Fn   func(*testing.B)
 }
 
-func (s *Suite) benchmarkFuncs(t testing.TB) (funcs []benchmarkFunction) {
+func (s *Suite[C]) benchmarkFuncs(t testing.TB) (funcs []benchmarkFunction) {
 	tpe := reflect.TypeOf(s)
 	v := reflect.ValueOf(s)
 
@@ -138,7 +138,7 @@ func (s *Suite) benchmarkFuncs(t testing.TB) (funcs []benchmarkFunction) {
 }
 
 // RunBenchmarks executes all defined benchmarks as subtests of b.
-func (s *Suite) RunBenchmarks(b *testing.B) {
+func (s *Suite[C]) RunBenchmarks(b *testing.B) {
 	var err error
 	s.Config, err = s.NewConfig()
 	if err != nil {
@@ -163,7 +163,7 @@ func (s *Suite) RunBenchmarks(b *testing.B) {
 	}
 }
 
-func (s *Suite) create(t testing.TB) restic.Backend {
+func (s *Suite[C]) create(t testing.TB) restic.Backend {
 	be, err := s.Create(s.Config)
 	if err != nil {
 		t.Fatal(err)
@@ -171,7 +171,7 @@ func (s *Suite) create(t testing.TB) restic.Backend {
 	return be
 }
 
-func (s *Suite) open(t testing.TB) restic.Backend {
+func (s *Suite[C]) open(t testing.TB) restic.Backend {
 	be, err := s.Open(s.Config)
 	if err != nil {
 		t.Fatal(err)
@@ -179,7 +179,7 @@ func (s *Suite) open(t testing.TB) restic.Backend {
 	return be
 }
 
-func (s *Suite) close(t testing.TB, be restic.Backend) {
+func (s *Suite[C]) close(t testing.TB, be restic.Backend) {
 	err := be.Close()
 	if err != nil {
 		t.Fatal(err)
diff --git a/internal/backend/test/tests.go b/internal/backend/test/tests.go
index a9514bf6b..b9dcc9ba5 100644
--- a/internal/backend/test/tests.go
+++ b/internal/backend/test/tests.go
@@ -38,7 +38,7 @@ func beTest(ctx context.Context, be restic.Backend, h restic.Handle) (bool, erro
 
 // TestCreateWithConfig tests that creating a backend in a location which already
 // has a config file fails.
-func (s *Suite) TestCreateWithConfig(t *testing.T) {
+func (s *Suite[C]) TestCreateWithConfig(t *testing.T) {
 	b := s.open(t)
 	defer s.close(t, b)
 
@@ -70,7 +70,7 @@ func (s *Suite) TestCreateWithConfig(t *testing.T) {
 }
 
 // TestLocation tests that a location string is returned.
-func (s *Suite) TestLocation(t *testing.T) {
+func (s *Suite[C]) TestLocation(t *testing.T) {
 	b := s.open(t)
 	defer s.close(t, b)
 
@@ -81,7 +81,7 @@ func (s *Suite) TestLocation(t *testing.T) {
 }
 
 // TestConfig saves and loads a config from the backend.
-func (s *Suite) TestConfig(t *testing.T) {
+func (s *Suite[C]) TestConfig(t *testing.T) {
 	b := s.open(t)
 	defer s.close(t, b)
 
@@ -118,7 +118,7 @@ func (s *Suite) TestConfig(t *testing.T) {
 }
 
 // TestLoad tests the backend's Load function.
-func (s *Suite) TestLoad(t *testing.T) {
+func (s *Suite[C]) TestLoad(t *testing.T) {
 	seedRand(t)
 
 	b := s.open(t)
@@ -223,7 +223,7 @@ func (s *Suite) TestLoad(t *testing.T) {
 }
 
 // TestList makes sure that the backend implements List() pagination correctly.
-func (s *Suite) TestList(t *testing.T) {
+func (s *Suite[C]) TestList(t *testing.T) {
 	seedRand(t)
 
 	numTestFiles := rand.Intn(20) + 20
@@ -326,7 +326,7 @@ func (s *Suite) TestList(t *testing.T) {
 }
 
 // TestListCancel tests that the context is respected and the error is returned by List.
-func (s *Suite) TestListCancel(t *testing.T) {
+func (s *Suite[C]) TestListCancel(t *testing.T) {
 	seedRand(t)
 
 	numTestFiles := 5
@@ -466,7 +466,7 @@ func (ec errorCloser) Rewind() error {
 }
 
 // TestSave tests saving data in the backend.
-func (s *Suite) TestSave(t *testing.T) {
+func (s *Suite[C]) TestSave(t *testing.T) {
 	seedRand(t)
 
 	b := s.open(t)
@@ -582,7 +582,7 @@ func (r *incompleteByteReader) Length() int64 {
 }
 
 // TestSaveError tests saving data in the backend.
-func (s *Suite) TestSaveError(t *testing.T) {
+func (s *Suite[C]) TestSaveError(t *testing.T) {
 	seedRand(t)
 
 	b := s.open(t)
@@ -621,7 +621,7 @@ func (b *wrongByteReader) Hash() []byte {
 }
 
 // TestSaveWrongHash tests that uploads with a wrong hash fail
-func (s *Suite) TestSaveWrongHash(t *testing.T) {
+func (s *Suite[C]) TestSaveWrongHash(t *testing.T) {
 	seedRand(t)
 
 	b := s.open(t)
@@ -679,7 +679,7 @@ func testLoad(b restic.Backend, h restic.Handle) error {
 	})
 }
 
-func (s *Suite) delayedRemove(t testing.TB, be restic.Backend, handles ...restic.Handle) error {
+func (s *Suite[C]) delayedRemove(t testing.TB, be restic.Backend, handles ...restic.Handle) error {
 	// Some backend (swift, I'm looking at you) may implement delayed
 	// removal of data. Let's wait a bit if this happens.
 
@@ -746,7 +746,7 @@ func delayedList(t testing.TB, b restic.Backend, tpe restic.FileType, max int, m
 }
 
 // TestBackend tests all functions of the backend.
-func (s *Suite) TestBackend(t *testing.T) {
+func (s *Suite[C]) TestBackend(t *testing.T) {
 	b := s.open(t)
 	defer s.close(t, b)
 
@@ -867,7 +867,7 @@ func (s *Suite) TestBackend(t *testing.T) {
 }
 
 // TestZZZDelete tests the Delete function. The name ensures that this test is executed last.
-func (s *Suite) TestZZZDelete(t *testing.T) {
+func (s *Suite[C]) TestZZZDelete(t *testing.T) {
 	if !test.TestCleanupTempDirs {
 		t.Skipf("not removing backend, TestCleanupTempDirs is false")
 	}