Added cursor tests

cursor/helper.go

@@ -6,7 +6,9 @@ import "io"
 // with limited backward seeking.
 type BufferedReaderAt struct{}
 
-func NewBufferedReaderAt(r io.Reader, minBuffer uint64) *BufferedReaderAt
+func NewBufferedReaderAt(r io.Reader, minBuffer uint64) *BufferedReaderAt {
+	return nil
+}
 
 // ReadAt reads bytes from the underlying reader. If the offset is after
 // the end of the buffer, ReadAt will first read and ignore bytes from the
@@ -15,7 +17,9 @@ func NewBufferedReaderAt(r io.Reader, minBuffer uint64) *BufferedReaderAt
 //
 // If your parser needs unlimited lookahead, you should probably
 // just read the whole input into a slice and use BytesCursor.
-func (b *BufferedReaderAt) ReadAt(dst []byte, offset int64) (int, error)
+func (b *BufferedReaderAt) ReadAt(dst []byte, offset int64) (int, error) {
+	return 0, nil
+}
 
 // RuneReader is an io.RuneReader backed by a Cursor, for compatibility
 // with the regexp package.