CheckCollector          An R6 class for collecting TestFileResult
                        objects during grading.
GradingResults          An R6 class representing a collection of test
                        case results
TestCase                An R6 class representing a test case
TestCaseResult          An R6 representing the results of running a
                        test case
TestFileResult          An R6 class representing a collection of test
                        case results
check                   Run the test cases in a test file
collector_env           An environment into which a collector will be
                        initialized (so we don't need to update global
                        variables).
collector_varname       The name of the active collector variable in
                        collector_env
execute_script          Generate an environment from an R script
export                  Export a submission to a zip file
get_collector           Retrieve the global CheckCollector
grade_script            Grade an R script against a series of test
                        files
initialize_collector    Create a new global CheckCollector
load_test_cases         Load test cases from a test file
make_secret             Generate a random string of characters
run_autograder          Grade an R script against test files in a
                        directory
update_ast_check_calls
                        Collect results of calls to 'ottr::check' in an
                        AST
valid_expr_chars        A string containing characters that can be made
                        into a valid variable name. Does not include
                        any digits because randomly sampling with them
                        included could result in an invalid variable
                        name.
valid_syntax            Check whether a string is valid R code
