tr := NewReader(f)
			for i, tc := range v.cases {
				hdr, err := tr.Next()
				if err != nil || hdr == nil {
					t.Fatalf("entry %d, Next(): got %v, want %v", i, err, nil)
				}
				buf := make([]byte, tc.cnt)
				if _, err := io.ReadFull(tr, buf); err != nil {
					t.Fatalf("entry %d, ReadFull(): got %v, want %v", i, err, nil)
				}
				if string(buf) != tc.output {