Unit testing record ggplot

[b-rodrigues]

It'd be great to unit test record ggplot

but testing plots is not easy. Maybe a snapshot test? See https://testthat.r-lib.org/articles/snapshotting.html

[b-rodrigues]

Since a ggplot is a list, maybe we could save the list as an rds file and expect_equal the save list from the rds with the freshly generated one? Could be easy