if w0 != 1 {
		t.Fatalf("write 1239 'x's: got %d writes, want 1", w0)
	}

	var w1 writeCountingDiscard
	b1 := NewWriterSize(&w1, 1234)
	b1.WriteString(strings.Repeat("x", 1200))
	b1.Flush()
	if w1 != 1 {
		t.Fatalf("flush 1200 'x's: got %d writes, want 1", w1)
	}
	b1.WriteString(strings.Repeat("x", 89))
	if w1 != 1 {
		t.Fatalf("write 1200 + 89 'x's: got %d writes, want 1", w1)
	}