This tests that the underlying value of a scale transformation
is 0. Since SMIL defines a by animation as being equivalent
to an additive values animation where the first value is zero and
the second value is the by value, such an animation would
begin by post-multiplying a scale(0) transformation to
the element's underlying transform list.
The test consists of two circles: an orange circle on the left,
which serves as a reference, and a blue circle on the right,
whose transform attribute is animated. Animation of
the circles begins at t=1s and lasts for 3s.
The transform animation that applies to the blue circle is of type
"scale", and specifies by="1". Since the animation is
considered to be equivalent to one that specifies from="0" to="1",
when the animation begins the circle will be scaled down to a point,
and then will be scaled up until it reaches its original size at
t=4s.
The test is passed if the blue circle on the right is always the same size as the orange circle on the left. The test runs from t=0s until t=4s.