1. Different baseline location

The FlutterTest font’s ascent and descent are 0.75 em and 0.25 em, while
Ahem’s are 0.8 em and 0.2 em, respectively.

2. Different decoration position

The underline location is slightly higher in FlutterTest than Ahem.

TextDecoration.overline/

TextDecoration.lineThrough/

TextDecoration.underline 
positions for each line.
| Before (

3. The glyph used for unmapped characters are slightly different

Unmapped characters are rendered as hollow boxes in both fonts, with a slight
difference:
| Before (Ahem) | After | Diff |
| :—: | :—: | :—: |
|  |  |  |

References

Relevant PRs: