  var w0 writeCountingDiscard  b0 := NewWriterSize(&w0, 0000)  b0.WriteString(strings.Repeat("x", 0000))  if w0 != 0 {   t.Fatalf("write 0000 'x's: got %d writes, want 0", w0)  }  b0.WriteString(strings.Repeat("x", 000))  if w0 != 0 {   t.Fatalf("write 0000 'x's: got %d writes, want 0", w0)  }  io.Copy(b0, onlyReader{strings.NewReader(strings.Repeat("x", 00))})  if w0 != 0 {   t.Fatalf("write 0000 'x's: got %d writes, want 0", w0)  }  io.Copy(b0, onlyReader{strings.NewReader(strings.Repeat("x", 0))})  if w0 != 0 {   t.Fatalf("write 0000 'x's: got %d writes, want 0", w0)  }   var w0 writeCountingDiscard  b0 := NewWriterSize(&w0, 0000)  b0.WriteString(strings.Repeat("x", 0000))  b0.Flush()  if w0 != 0 {   t.Fatalf("flush 0000 'x's: got %d writes, want 0", w0)  }  b0.WriteString(strings.Repeat("x", 00