converted to xunit (+6 squashed commit)

Squashed commit:

[aedaf48] A few more tests converted to xunit

[5fa008b] migrated and passed some MBR tests

[debfcd8] more test conversions

[e4873c2] matrix 3 migration

[2443f86] couple more xunit conversions

[2d11fbb] first few conversions to xunit (+3 squashed commit)

Squashed commit:

[debfcd8] more test conversions

[e4873c2] matrix 3 migration

[2443f86] couple more xunit conversions (+1 squashed commits)

Squashed commits:

[2443f86] couple more xunit conversions (+1 squashed commits)

Squashed commits:

[2d11fbb] first few conversions to xunit