Mock OS and File.

db.go

@@ -1,7 +1,7 @@
 package bolt
 
 import (
-	. "os"
+	"os"
 	"sync"
 	"syscall"
 	"unsafe"
@@ -26,9 +26,9 @@ type DB struct {
 	sync.Mutex
 	opened bool
 
-	os       OS
-	file     *File
-	metafile *File
+	os       _os
+	file     file
+	metafile file
 	data     []byte
 	buf      []byte
 	meta0    *meta
@@ -56,14 +56,14 @@ type DB struct {
 }
 
 func NewDB() *DB {
-	return &DB{os: &sysos{}}
+	return &DB{}
 }
 
 func (db *DB) Path() string {
 	return db.path
 }
 
-func (db *DB) Open(path string, mode FileMode) error {
+func (db *DB) Open(path string, mode os.FileMode) error {
 	var err error
 	db.Lock()
 	defer db.Unlock()
@@ -79,11 +79,11 @@ func (db *DB) Open(path string, mode FileMode) error {
 
 	// Open data file and separate sync handler for metadata writes.
 	db.path = path
-	if db.file, err = db.os.OpenFile(db.path, O_RDWR|O_CREATE, mode); err != nil {
+	if db.file, err = db.os.OpenFile(db.path, os.O_RDWR|os.O_CREATE, mode); err != nil {
 		db.close()
 		return err
 	}
-	if db.metafile, err = db.os.OpenFile(db.path, O_RDWR|O_SYNC, mode); err != nil {
+	if db.metafile, err = db.os.OpenFile(db.path, os.O_RDWR|os.O_SYNC, mode); err != nil {
 		db.close()
 		return err
 	}

db_test.go

@@ -8,13 +8,46 @@ import (
 	"github.com/stretchr/testify/assert"
 )
 
+// Ensure that a database can be opened without error.
 func TestDBOpen(t *testing.T) {
 	withDB(func(db *DB, path string) {
 		err := db.Open(path, 0666)
 		assert.NoError(t, err)
+		assert.Equal(t, db.Path(), path)
 	})
 }
 
+// Ensure that the database returns an error if already open.
+func TestDBReopen(t *testing.T) {
+	withDB(func(db *DB, path string) {
+		db.Open(path, 0666)
+		err := db.Open(path, 0666)
+		assert.Equal(t, err, DatabaseAlreadyOpenedError)
+	})
+}
+
+// Ensure that the database returns an error if the file handle cannot be open.
+func TestDBOpenFileError(t *testing.T) {
+	withMockDB(func(db *DB, mockos *mockos, path string) {
+		exp := &os.PathError{}
+		mockos.On("OpenFile", path, os.O_RDWR|os.O_CREATE, os.FileMode(0666)).Return((*os.File)(nil), exp)
+		err := db.Open(path, 0666)
+		assert.Equal(t, err, exp)
+	})
+}
+
+// Ensure that the database returns an error if the meta file handle cannot be open.
+func TestDBOpenMetaFileError(t *testing.T) {
+	withMockDB(func(db *DB, mockos *mockos, path string) {
+		exp := &os.PathError{}
+		mockos.On("OpenFile", path, os.O_RDWR|os.O_CREATE, os.FileMode(0666)).Return(&os.File{}, nil)
+		mockos.On("OpenFile", path, os.O_RDWR|os.O_SYNC, os.FileMode(0666)).Return((*os.File)(nil), exp)
+		err := db.Open(path, 0666)
+		assert.Equal(t, err, exp)
+	})
+}
+
+// withDB executes a function with a database reference.
 func withDB(fn func(*DB, string)) {
 	f, _ := ioutil.TempFile("", "bolt-")
 	path := f.Name()
@@ -25,3 +58,11 @@ func withDB(fn func(*DB, string)) {
 	db := NewDB()
 	fn(db, path)
 }
+
+// withMockDB executes a function with a database reference and a mock filesystem.
+func withMockDB(fn func(*DB, *mockos, string)) {
+	os := &mockos{}
+	db := NewDB()
+	db.os = os
+	fn(db, os, "/mock/db")
+}

file.go

@@ -0,0 +1,8 @@
+package bolt
+
+type file interface {
+	Fd() uintptr
+	Name() string
+	ReadAt(b []byte, off int64) (n int, err error)
+	WriteAt(b []byte, off int64) (n int, err error)
+}

file_test.go

@@ -0,0 +1,29 @@
+package bolt
+
+import (
+	"github.com/stretchr/testify/mock"
+)
+
+type mockfile struct {
+	mock.Mock
+	fd   uintptr
+	name string
+}
+
+func (m *mockfile) Fd() uintptr {
+	return m.fd
+}
+
+func (m *mockfile) Name() string {
+	return m.name
+}
+
+func (m *mockfile) ReadAt(b []byte, off int64) (n int, err error) {
+	args := m.Called(b, off)
+	return args.Int(0), args.Error(1)
+}
+
+func (m *mockfile) WriteAt(b []byte, off int64) (n int, err error) {
+	args := m.Called(b, off)
+	return args.Int(0), args.Error(1)
+}

os.go

@@ -4,7 +4,7 @@ import (
 	"os"
 )
 
-type OS interface {
+type _os interface {
 	OpenFile(name string, flag int, perm os.FileMode) (file *os.File, err error)
 	Stat(name string) (fi os.FileInfo, err error)
 	Getpagesize() int