tests: []testFnc{
			testWrite{"ab", 2, nil},
			testRemaining{6, 3},
			testReadFrom{fileOps{int64(3), "cde"}, 6, nil},
			testRemaining{0, 0},
		},
	}, {
		maker: makeSparse{makeReg{5, "abcde"}, sparseHoles{{2, 3}}, 8},
		tests: []testFnc{
			testReadFrom{fileOps{"ab", int64(3), "cde"}, 8, nil},
			testRemaining{0, 0},
		},
	}, {
		maker: makeSparse{makeReg{5, "abcde"}, sparseHoles{{2, 3}}, 8},