tw := NewWriter(&buf)
			for _, file := range v.files {
				tw.WriteHeader(file.hdr)
				tw.Write(file.body)
			}
			tw.Close()
			b.Run(v.label, func(b *testing.B) {
				b.ReportAllocs()
				// Read from the byte buffer.
				for i := 0; i < b.N; i++ {
					r.Reset(buf.Bytes())
					tr := NewReader(&r)
					if _, err := tr.Next(); err != nil {
						b.Errorf("unexpected Next error: %v", err)
					}