Suggested packages should be used conditionally

[aravindhebbali]

* checking tests ... ERROR
   Running 'testthat.R'
Running the tests in 'tests/testthat.R' failed.
Complete output:
   > # This file is part of the standard setup for testthat.
   > # It is recommended that you do not modify it.
   > #
   > # Where should you do additional test configuration?
   > # Learn more about the roles of various files in:
   > # * https://r-pkgs.org/tests.html
   > # *
https://testthat.r-lib.org/reference/test_package.html#special-files
   >
   > library(testthat)
   > library(yahoofinancer)
   >
   > test_check("yahoofinancer")
   Error in `FUN()`:
   ! In path:
"D:\\library-devel\\yahoofinancer.Rcheck\\tests\\testthat\\setup.R"
   Caused by error in `library()`:
   ! there is no package called 'httptest'
   Backtrace:
        ▆
     1. ├─testthat::test_check("yahoofinancer")
     2. │ └─testthat::test_dir(...)
     3. │   └─testthat:::test_files(...)
     4. │     └─testthat:::test_files_serial(...)
     5. │       └─testthat:::test_files_setup_state(...)
     6. │         └─testthat::source_test_setup(".", env)
     7. │           └─testthat::source_dir(path, "^setup.*\\.[rR]$", env
= env, wrap = FALSE)
     8. │             └─base::lapply(...)
     9. │               └─testthat (local) FUN(X[[i]], ...)
    10. │                 └─testthat::source_file(path, env = env, chdir
= chdir, wrap = wrap)
    11. │                   ├─base::withCallingHandlers(...)
    12. │                   └─base::eval(exprs, env)
    13. │                     └─base::eval(exprs, env)
    14. │                       └─base::library(httptest) at
D:\library-devel\yahoofinancer.Rcheck\tests\testthat\setup.R:1:1
    15. │
└─base::stop(packageNotFoundError(package, lib.loc, sys.call()))
    16. └─testthat (local) `<fn>`(`<pckgNtFE>`)
    17.   └─rlang::abort(...)
   Execution halted