This test makes sure that ruby inside text-align: justify has its contents justified.
<div style="text-align: justify; font-size: 16px;">
<div>
abcdefg abcdefg mmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmm
</div>
<div>
abcdefg abcdefg abcdefg mmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmm
</div>
<div>
abcdefg <ruby>abcdefg<rt><span style="color: transparent;">a</span></ruby> abcdefg mmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmm
</div>
<div>
abcdefg <ruby>a<rt><span style="color: transparent;">a</span></ruby> abcdefg mmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmm
</div>
<div>
a<span">&#x685c;</span>b mmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmm
</div>
</div>
<div style="font-family: Ahem; font-size: 16px;">
<ruby>abcdefg&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;abcdefg<rt>a</ruby> mmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmm
</div>
<div style="text-align: right;">
a
</div>
<div style="text-align: justify;">
abcdefg abcdefg mmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmm
</div>