Test that fails when devtools isn't installed

[hadley]

from @s-u

1. Error: can mock if package is not loaded ------------------------------------
there is no package called 'devtools'
1: withCallingHandlers(eval(code, new_test_environment), error = capture_calls)
2: eval(code, new_test_environment)
3: eval(expr, envir, enclos)
4: with_mock(`devtools::add_path` = identity, expect_identical(devtools::add_path, identity)) at test-mock.r:120
5: extract_mocks(new_values = new_values[!code_pos], .env = .env)
6: lapply(setNames(nm = mock_qual_names), function(qual_name) {
       pkg_name <- gsub(pkg_and_name_rx, "\\1", qual_name)
       name <- gsub(pkg_and_name_rx, "\\2", qual_name)
       if (pkg_name == "")
           pkg_name <- .env
       env <- asNamespace(pkg_name)
       if (!exists(name, envir = env, mode = "function"))
           stop("Function ", name, " not found in environment ", environmentName(env),
               ".")
       mock(name = name, env = env, new = eval(new_values[[qual_name]]))
   })
7: FUN(X[[i]], ...)
8: asNamespace(pkg_name)
9: getNamespace(ns)
10: tryCatch(loadNamespace(name), error = function(e) stop(e))
11: tryCatchList(expr, classes, parentenv, handlers)
12: tryCatchOne(expr, names, parentenv, handlers[[1L]])
13: value[[3L]](cond)

Error: Test failures
Execution halted

@krlmlr can you please take a look?

[jimhester]

I know I am not Kirill, but it looks like adding the following before tests/testthat/test-mock.r#L119-L121 should fix this

if (!"devtools" %in% installed.packages()[, "Package"])
  skip("devtools is not installed")

[s-u]

FWIW installed.packages() is not cheap so it may be faster to use

if (!length(find.package("devtools", quiet=TRUE)))

[krlmlr]

Thanks, @jimhester and @s-u.