Add more unit tests

[donyunardi]

Feature description

Please add unit tests for these functions:

• requirement #0.01 'Add empty choice to choices selected' is not covered by
  any test

teal.transform/R/choices_selected.R

Lines 201 to 223 in 14cf71e

	#' Add empty choice to choices selected
	#'
	#' @param x (`choices_selected`) object.
	#' @param multiple (`logical(1)`) whether multiple selections are allowed or not.
	#'
	#' @return `choices_selected` object with an empty option added to the choices.
	#'
	#' @export
	#'
	add_no_selected_choices <- function(x, multiple = FALSE) {
	if (is.null(x)) {
	choices_selected(NULL)
	} else {
	stopifnot(is.choices_selected(x))
	if (!multiple) {
	x$choices <- c(no_select_keyword, x$choices)
	if (is.null(x$selected)) x$selected <- no_select_keyword
	}
	x
	}
	}

• requirement #0.10 'Help text with available datasets input' is not covered
  by any test

teal.transform/R/data_extract_datanames.R

Lines 1 to 20 in 14cf71e

	#' Help text with available datasets input
	#'
	#' @description
	#'
	#' Creates [shiny::helpText()] with the names of available datasets for the
	#' current module.
	#'
	#' @param data_extracts (`list`) of data extracts for single variable.
	#'
	#' @return `shiny.tag` defining help-text element that can be added to a UI element.
	#'
	#' @export
	#'
	datanames_input <- function(data_extracts) {
	datanames <- get_extract_datanames(data_extracts)
	helpText(
	paste0("Dataset", `if`(length(datanames) > 1, "s", ""), ":"),
	tags$code(paste(datanames, collapse = ", "))
	)
	}

• requirement #0.15 'Returns non-key column names from data' is not covered
  by any test

teal.transform/R/column_functions.R

Lines 1 to 20 in 14cf71e

	#' Returns non-key column names from data
	#'
	#' @description Returns non-key column names from data.
	#'
	#' @param data (`data.frame`) Data with attribute `filter_and_columns`. This can only be
	#' created by [data_extract_srv()], which returns a shiny [shiny::reactive()].
	#'
	#' @return A named `character` vector with the non-key columns of the `data`.
	#'
	#' @references [data_extract_srv()]
	#'
	#' @export
	#'
	get_dataset_prefixed_col_names <- function(data) {
	if (!is.null(attr(data, "filter_and_columns")$columns) && attr(data, "filter_and_columns")$columns != "") {
	paste(attr(data, "dataname"), attr(data, "filter_and_columns")$columns, sep = ".")
	} else {
	NULL
	}
	}

• requirement #0.19 'Verify uniform dataset source across data extract
  specification' is not covered by any test

teal.transform/R/data_extract_datanames.R

Lines 65 to 83 in 14cf71e

	#' Verify uniform dataset source across data extract specification
	#'
	#' @description
	#'
	#' Checks if the input `data_extract_spec` objects all come from the same dataset.
	#'
	#' @param ... either `data_extract_spec` objects or lists of `data_extract_spec`
	#' objects that do not contain `NULL`
	#'
	#' @return `TRUE` if all `data_extract_spec` objects come from the same dataset,
	#' `FALSE` otherwise.
	#'
	#' @export
	#'
	is_single_dataset <- function(...) {
	data_extract_spec <- list(...)
	dataset_names <- get_extract_datanames(data_extract_spec)
	length(dataset_names) == 1
	}

• requirement #0.24 'Check select choices for no choice made' is not covered
  by any test

teal.transform/R/choices_selected.R

Lines 225 to 239 in 14cf71e

	#' Check select choices for no choice made
	#'
	#' @param x (`character`) Word that shall be checked for `NULL`, empty, "--no-selection".
	#'
	#' @return The word or `NULL`.
	#'
	#' @export
	#'
	no_selected_as_NULL <- function(x) { # nolint: object_name_linter.
	if (is.null(x) || identical(x, no_select_keyword) || x == "") {
	NULL
	} else {
	x
	}
	}

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