Test Backup misuse.

backup.go

@@ -53,6 +53,9 @@ type Backup struct {
 // Copy up to N pages between the source and destination databases
 // (See http://sqlite.org/c3ref/backup_finish.html#sqlite3backupstep)
 func (b *Backup) Step(npage int) error {
+	if b == nil {
+		return ErrMisuse
+	}
 	rv := C.sqlite3_backup_step(b.sb, C.int(npage))
 	if rv == C.SQLITE_OK || Errno(rv) == ErrBusy || Errno(rv) == ErrLocked { // TODO Trace busy/locked errors
 		return nil
@@ -101,6 +104,9 @@ func (b *Backup) Run(npage int, sleepNs time.Duration, c chan<- BackupStatus) er
 // Finish/stop the backup
 // (See http://sqlite.org/c3ref/backup_finish.html#sqlite3backupfinish)
 func (b *Backup) Close() error {
+	if b == nil {
+		return ErrMisuse
+	}
 	rv := C.sqlite3_backup_finish(b.sb)
 	if rv != C.SQLITE_OK {
 		return Errno(rv)

backup_test.go

@@ -24,4 +24,21 @@ func TestBackup(t *testing.T) {
 	}()
 	err = bck.Run(10, 0, cbs)
 	checkNoError(t, err, "couldn't do backup: %#v")
+
+	err = bck.Close()
+	checkNoError(t, err, "couldn't close backup twice: %#v")
+}
+
+func TestBackupMisuse(t *testing.T) {
+	db := open(t)
+	defer db.Close()
+
+	bck, err := NewBackup(db, "main", db, "main")
+	if bck != nil || err == nil {
+		t.Error("source and destination must be distinct")
+	}
+	err = bck.Run(10, 0, nil)
+	if err == nil {
+		t.Error("Misuse expected")
+	}
 }