R/generate_tests.R

In pgcudahy/advRkoans: A tutorial for learning Advanced R by making tests pass

answers <- list(
    about_expectations = list(
        "expect truth" = c("TRUE"),
        "expect with messages" = c("TRUE"),
        "fill in values" = c("2"),
        "expect equality" = c("expected_value"),
        "a better way of asserting equality" = c("expected_value")),
    about_binding_basics = list(
        "names have values" = c("c(1, 2, 3)"),
        "names can reference existing objects" = c("y"),
        "names with the same values can be different objects" = c("b", "c", "d",
            "b", "c", "lobstr::obj_addr(d)"),
        "many ways of accessing functions point to the same object" = c("1"),
        "names have rules" = c('"unexpected input"', '"unexpected assignment"',
            '"invalid (do_set) left-hand side to assignment", fixed=TRUE'),
        "rules can be broken" = c("`_abc`", "`if`"),
        "double quotes are not a good option" = c('get("_abc")', 'get("if")'),
        "make.names() is irreversible" =
            c('"X"', '"A."', '"if."', '"if."', '"if"')),
    about_copy_on_modify = list(
        "R performs copy on modify" = c("lobstr::obj_addr(y)"),
        "tracemem() can show when an object is copied" = c('"^tracemem"', "NA"),
        "tracemem is not useful on unnamed objects" = c("NA"),
        "modifying a vector element triggers a copy" = c("1", "2"),
        "copy-on-modify applies to function calls" = c("NA", '"^tracemem"'),
        "elements of lists point to values" = c("new_element1_address",
            "new_element2_address"),
        "lists are shallow copies" = c("list2_element1_address",
            "list2_element2_address", "list2_element3_address"),
        "lists can nest shallow copies" = c("b[[1]]", "c[[2]]", "c[[1]]"),
        "lists can reference themselves" = c("x[[2]][1]"),
        "data frames are lists of vectors" = c("d2$x",
            "lobstr::obj_addr(d2$y)", "c(FALSE, FALSE, FALSE)"),
        "a character vector is a vector of strings, not individual characters" =
            c("lobstr::obj_addrs(y)[2]", "lobstr::obj_addrs(y)[1]"))
    )

generate_tests <- function() {
    lessons <- koans_df$lesson_file
    tests <- purrr::map(lessons, function(x) readChar(x, file.info(x)$size))
    new_tests <- purrr::map2(tests, answers,
        function(x, y) purrr::reduce(as.vector(unlist(y)),
            function(a, b) sub("`_*_`", b, a), .init = x))
    purrr::walk2(new_tests, koans_df$test_file,
        function(x, y) writeLines(x, con = y))
}