Add test for tts:textEmphasis='auto'

[palemieux]

No description provided.

[cconcolato]

It is very hard to see anything on the images 0.000000.png and 0.040000.png. Can we increase the contrast? And image 0.080000.png is completely blank. Is it on purpose?
Could we add some metadata in the test to indicate what it is for?

[palemieux]

It is very hard to see anything on the images 0.000000.png and 0.040000.png. Can we increase the contrast?

As requested.

Could we add some metadata in the test to indicate what it is for?

As requested.

And image 0.080000.png is completely blank. Is it on purpose?

Yes. All tests include the entire timeline, from 0s to infinity.

[cconcolato]

We could also have:
tts:textEmphasis='auto' (default positioning)
and
tts:textEmphasis='auto outside' (explicit positioning, equivalent to default)

[nigelmegitt]

The contrast still looks very low to me - could we perhaps use a solid colour instead of outline, or make the outline thicker?