You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: ycbcr_test.go
    path of file: ./repos/gccrs/libgo/go/image
    
    the code of the file until where you have to start completion: // Copyright 2012 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package image

import (
	"image/color"
	"testing"
)

func TestYCbCr(t *testing.T) {
	rects := []Rectangle{
		Rect(0, 0, 16, 16),
		Rect(1, 0, 16, 16),
		Rect(0, 1, 16, 16),
		Rect(1, 1, 16, 16),
		Rect(1, 1, 15, 16),
		Rect(1, 1, 16, 15),
		Rect(1, 1, 15, 15),
		Rect(2, 3, 14, 15),
		Rect(7, 0, 7, 16),
		Rect(0, 8, 16, 8),
		Rect(0, 0, 10, 11),
		Rect(5, 6, 16, 16),
		Rect(7, 7, 8, 8),
		Rect(7, 8,
    
func testYCbCr(t *testing.T, r Rectangle, subsampleRatio YCbCrSubsampleRatio, delta Point) {
	// Create a YCbCr image m, whose bounds are r translated by (delta.X, delta.Y).
	r1 := r.Add(delta)
	m := NewYCbCr(r1, subsampleRatio)

	// Test that the image buffer is reasonably small even if (delta.X, delta.Y) is far from the origin.
	if len(m.Y) > 100*100 {
		t.Errorf("r=%v, subsampleRatio=%v, delta=%v: image buffer is too large",
			r, subsampleRatio, delta)
		return
	}

	// Initialize m's pixels. For 422 and 420 subsampling, some of the Cb and Cr elements
	// will be set multiple times. That's OK. We just want to avoid a uniform image.
	for y := r1.Min.Y; y < r1.Max.Y; y++ {
		for x := r1.Min.X; x < r1.Max.X; x++ {
			yi := m.YOffset(x, y)
			ci := m.COffset(x, y)
			m.Y[yi] = uint8(16*y + x)
			m.Cb[ci] = uint8(y + 16*x)
			m.Cr[ci] = uint8(y + 16*x)
		}
	}

	// Make various sub-images of m.
	for y0 := delta.Y + 3; y0 < delta.Y+7; y0++ {
		for y1 := delta.Y + 8; y1 < delta.Y+13; y1++ {
			for x0 := delta.X + 3; x0 < delta.X+7; x0++ {
				for x1 := delta.X + 8; x1 < delta.X+13; x1++ {
					subRect := Rect(x0, y0, x1, y1)
					sub := m.SubImage(subRect).(*YCbCr)

					// For each point in the sub-image's bounds, check that m.At(x, y) equals sub.At(x, y).
					for y := sub.Rect.Min.Y; y < sub.Rect.Max.Y; y++ {
						for x := sub.Rect.Min.X; x < sub.Rect.Max.X; x++ {
							color0 := m.At(x, y).(color.YCbCr)
							color1 := sub.At(x, y).(color.YCbCr)
							if color0 != color1 {
								t.Errorf("r=%v, subsampleRatio=%v, delta=%v, x=%d, y=%d, color0=%v, color1=%v",
									r, subsampleRatio, delta, x, y, color0, color1)
								return
							}
						}
					}
				}
			}
		}
	}
}