…gative values

… of tests()) and regenerates reference files; passes all tests on second run of tests(); not committing new reference files

…_value() with update=FALSE; note that there is a bug in expect_equal_to_reference() such that update is reset from FALSE to TRUE (see testthat issue 683)

…s; need input from @thibautjombart on what expected behavior should be

…sired behaviour as a result of the change to doubling / halving interval CIs; committing new reference rds files

…it together; add test for this

…ups that have growth rates with different signs

…fits (see previous commit)