 if (validFilters(gl[magFilter], gl[minFilter])) {
                                    wtu.checkCanvasRect(gl, 0, 0, 1, 1, [170, 0, 0, 1], "sampling stencil from complete texture", 1);
                                } else {
                                    // Incomplete textures may produce [0, 0, 0, 1] or [0, 0, 0, 255].
                                    const value = new Uint8Array(4);
                                    gl.readPixels(0, 0, 1, 1, gl.RGBA, gl.UNSIGNED_BYTE, value);
                 