test_that("vector of destination codes", {
    expect_equal(countrycode("Serbia", "country.name", "iso3c"), "SRB")
    expect_warning(expect_equal(countrycode("Serbia", "country.name", "cowc"), NA_character_))
    expect_warning(expect_equal(countrycode("Serbia", "country.name", c("cowc", "iso3c")), "SRB"))
})