Make sure that getBufferSubData() doesn't work on WebGL 1 contexts On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE". PASS context.getError() is context.NO_ERROR PASS context.getError() is context.NO_ERROR PASS context.getError() is context.NO_ERROR PASS context.getError() is context.NO_ERROR PASS receiver[0] is fullArrayView[0] PASS receiver[1] is fullArrayView[1] PASS receiver[2] is fullArrayView[2] PASS receiver[3] is fullArrayView[3] PASS receiver[4] is fullArrayView[4] PASS receiver[5] is fullArrayView[5] PASS receiver[6] is fullArrayView[6] PASS receiver[7] is fullArrayView[7] PASS receiver[8] is fullArrayView[8] PASS receiver[9] is fullArrayView[9] PASS context.getError() is context.NO_ERROR PASS context.getError() is context.NO_ERROR PASS context.getError() is context.NO_ERROR PASS context.getError() is context.NO_ERROR PASS context.getBufferSubData(context.ARRAY_BUFFER, 0, receiver, 0, 10) threw exception TypeError: context.getBufferSubData is not a function. (In 'context.getBufferSubData(context.ARRAY_BUFFER, 0, receiver, 0, 10)', 'context.getBufferSubData' is undefined). PASS context.getError() is context.NO_ERROR PASS context is null PASS successfullyParsed is true TEST COMPLETE