f.ops = f.ops[1:]
	return f.pos, nil
}

func equalSparseEntries(x, y []sparseEntry) bool {
	return (len(x) == 0 && len(y) == 0) || reflect.DeepEqual(x, y)
}

func TestSparseEntries(t *testing.T) {
	vectors := []struct {
		in   []sparseEntry
		size int64

		wantValid    bool          // Result of validateSparseEntries
		wantAligned  []sparseEntry // Result of alignSparseEntries

			ops     fileOps
			wantCnt int64
			wantErr error
		}
		testClose struct { // Close() == wantErr
			wantErr error
		}
		testFnc any // testHeader | testWrite | testReadFrom | testClose
	)

	vectors := []struct {
		file  string // Optional filename of expected output
		tests []testFnc
	}{{
		// The writer test file was produced with this command:
		// tar (GNU tar) 1.26
		//   ln -s small.txt link.txt