Window tests are incomplete

[Orace]

Actually Window test doesn't cover

• enumerator disposal (in Return isolated windows from Window* methods #655)
• MoveNext calls after enumerator end (in Return isolated windows from Window* methods #655)
• Returned Window are isolated from each others (see Windows of Window(Left|Right) are not isolated from each other #652) (in Return isolated windows from Window* methods #655)
• Test Window method on known results (in Return isolated windows from Window* methods #655)
• Test WindowLeft method on known results (in Refactor Window(Left|Right) #656)
• Test WindowRight method on known results (in Refactor Window(Left|Right) #656)

[Orace]

All those tests are implemented in #653
They don't pass because of #652

[Orace]

All those tests pass in #655

[Orace]

Fixed with #655