Enhance test coverage for call_derivation(), derive_vars_merged(), get_not_mapped()

[manciniedoardo]

Background Information

It would be great to get {admiral}'s test coverage to 100%. However, this should not come at the expense of development time/effort from {admiral} core developers. As such, I have made a set of issues tagged "Unit Tests" (such as this one for call_derivation(), derive_vars_merged() and get_not_mapped()) where users who wish to dip their feet into the {admiral} ecosystem can:

• Learn a bit about unit testing for R packages
• Make a meaningful contribution to {admiral}

by adding or modifying unit tests to account for lines not previously covered.

Important note: Given the above, this issue is for newcomers to {admiral} or users who wish to contribute to the package, and should not be taken on by core {admiral} developers.

Definition of Done

• Unit test(s) added/modified to test the lines in red in call_derivation():
  

• Unit test(s) added/modified to test the lines in red in derive_vars_merged():
  

• Unit test(s) added/modified to test the lines in red in get_not_mapped():
  

[bms63]

@manciniedoardo We might want to break these up into individual issues?

I think some of this environment handling tests are not easy - perhaps that is why there is no coverage of them

[jimrothstein]

line # 783: get_not_mapped() - Goal: get this function to run (code coverage).

(Trying to find another way to explain this ....)

Work backwards:

line # 761 must run
line # 749 df temp_not_mapped must have rows
line # 746 unless tmp_lookup_flag is NA; runs filter(F) returns no rows.
line # 729 tmp_lookup_flag is set and NEVER NULL or NA

In debug, I reset tmp_lookup_flag ... to get call to get_not_mapped()

---