backend/test: remove duplicate test

The test is identical to the tests for the mem backend.

internal/backend/test/tests_test.go

@@ -1,66 +0,0 @@
-package test_test
-
-import (
-	"context"
-	"testing"
-
-	"github.com/restic/restic/internal/errors"
-	"github.com/restic/restic/internal/restic"
-
-	"github.com/restic/restic/internal/backend/mem"
-	"github.com/restic/restic/internal/backend/test"
-)
-
-type memConfig struct {
-	be restic.Backend
-}
-
-func newTestSuite(t testing.TB) *test.Suite {
-	return &test.Suite{
-		// NewConfig returns a config for a new temporary backend that will be used in tests.
-		NewConfig: func() (interface{}, 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 {
-				ok, err := c.be.Test(context.TODO(), restic.Handle{Type: restic.ConfigFile})
-				if err != nil {
-					return nil, err
-				}
-
-				if ok {
-					return nil, errors.New("config already exists")
-				}
-			}
-
-			c.be = mem.New()
-			return c.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()
-			}
-			return c.be, nil
-		},
-
-		// CleanupFn removes data created during the tests.
-		Cleanup: func(cfg interface{}) error {
-			// no cleanup needed
-			return nil
-		},
-	}
-}
-
-func TestSuiteBackendMem(t *testing.T) {
-	newTestSuite(t).RunTests(t)
-}
-
-func BenchmarkSuiteBackendMem(b *testing.B) {
-	newTestSuite(b).RunBenchmarks(b)
-}