The example code that is meant to be XIncluded into the API reference
should not be part of the interactive test suite: it's code that it is
meant to be used as a reference implementation - whereas the interactive
test suite should be allowed to be lean and test behaviour even in nasty
ways. In short: the test suite should not be the place where we show off
idiomatic code for educational purposes.
Both ClutterCanvas and ClutterImage should use the minification and
magnification filters set on the actor, just like the use the content
box and the paint opacity.
