Rewrites test assertions to use refute and assert where appropriate.

Transformations

• assert not expr becomes refute expr
• assert !expr becomes refute expr
• refute not expr becomes assert expr
• refute !expr becomes assert expr

Examples

# Before
assert not user.active?
assert !valid?
refute not user.inactive?
refute !invalid?

# After
refute user.active?
refute valid?
assert user.inactive?
assert invalid?