DONE:
test1: multiple sheets that have formula dependency from one to another
test2: multiple sheets that have formula dependency from one to another (with undo/redo)
test3: multiple sheets that have formulas dependencies from one to another
test4: multiple sheets that have formulas dependencies from one to another (with undo/redo)
test5: yanking and pasting ents keeping references (Pc) - timing and memory usage
test6: yanking and pasting ents keeping references (Pc) - with undo
test8: delete columns and rows repeatedly with undo.
test9: delete last alloc'ed column (ZZ) with undo.

TODO:
+ test7: yanking and pasting ents keeping references (Pc) (with undo and redo)
fails to restore some ents formulas.

+ test10: copiar un rango de 10filas x 1 columna con
referencias y pegar en la misma ubicación con Pv daba segfault. crear prueba.