for _, growLen := range []int{0, 100, 1000, 10000, 100000} {
		for _, startLen := range []int{0, 100, 1000, 10000, 100000} {
			xBytes := Repeat(x, startLen)

			buf := NewBuffer(xBytes)
			// If we read, this affects buf.off, which is good to test.
			readBytes, _ := buf.Read(tmp)
			yBytes := Repeat(y, growLen)
			allocs := testing.AllocsPerRun(100, func() {
				buf.Grow(growLen)
				buf.Write(yBytes)
			})

==============================

Before updating vendor directories, ensure that module mode is enabled.
Make sure that GO111MODULE is not set in the environment, or that it is
set to 'on' or 'auto', and if you use a go.work file, set GOWORK=off.

Requirements may be added, updated, and removed with 'go get'.
The vendor directory may be updated with 'go mod vendor'.
A typical sequence might be:

    cd src  # or src/cmd
    go get golang.org/x/net@master

	}
	buf := make([]byte, ss.Size())
	for off := int64(0); off < ss.Size(); off++ {
		for size := 1; size <= int(ss.Size()-off); size++ {
			readBuf := buf[:size]
			n, err := ss.ReadAt(readBuf, off)
			if off < ss.Size()-keep {
				if err != errDiscardedBytes {
					t.Errorf("off %d, size %d = %v, %v (%q); want errDiscardedBytes", off, size, n, err, readBuf[:n])
				}
				continue
			}