For this test we are using two fonts. AhemEx500 has a aspect value (xHeight/size) of 0.5 and AhemEx250 an aspect value of 0.25. On both fonts all glyphs used in the tests look like a square but AhemEx500 doesn't contain 'A' (U+0041).
1. Same glyph x in different spans with different fonts. The second one is adjusted with font-size-adjust. They should have the same size for test to pass.
xx
2. Different glyphs 'x' and 'A' in the same span, with 2 fonts in font-family fallback and without font-size-adjust. The second glyph can't be rendered by primary font so it will individually fallback to the secondary font. Note it is smaller than the first glyph.
xA
3. Different glyphs 'x' and 'A' in the same span, with 2 fonts in font-family fallback and with font-size-adjust. The second glyph can't be rendered by primary font so it will individually fallback to the secondary font. Note that now they have the same size.
xx