return nil, nil
		}
	}

	for _, tc := range trimTests {
		name := tc.f
		f, fb := toFn(name)
		if f == nil && fb == nil {
			continue
		}
		var actual string
		if f != nil {
			actual = string(f([]byte(tc.in), tc.arg))
		} else {
			actual = string(fb([]byte(tc.in), []byte(tc.arg)))
		}
		if actual != tc.out {

	full, frag, n, err := b.collectFragments(delim)
	// Allocate new buffer to hold the full pieces and the fragment.
	var buf strings.Builder
	buf.Grow(n)
	// Copy full pieces and fragment in.
	for _, fb := range full {
		buf.Write(fb)
	}
	buf.Write(frag)
	return buf.String(), err
}

// WriteTo implements io.WriterTo.
// This may make multiple calls to the [Reader.Read] method of the underlying [Reader].