Add assert_count_true() to verify that an expected number of values…

… are `TRUE`

NAMESPACE

@@ -29,6 +29,7 @@ export(adorn_rounding)
 export(adorn_title)
 export(adorn_totals)
 export(as_tabyl)
+export(assert_count_true)
 export(chisq.test)
 export(clean_names)
 export(compare_df_cols)

NEWS.md

@@ -14,6 +14,8 @@ These are all minor breaking changes resulting from enhancements and are not exp
 
 * The new function `excel_time_to_numeric()` converts times from Excel that do not have accompanying dates into a number of seconds.  (#245, thanks to **@billdenney** for the feature.)
 
+* The new function `assert_count_true()` verifies that an expected number of values are `TRUE` for quality checks in data pipelines
+
 ## Bug fixes
 
 * `adorn_totals("row")` now succeeds if the new `name` of the totals row is already a factor level of the input data.frame (#529, thanks @egozoglu for reporting).

R/assert_count_true.R

@@ -0,0 +1,30 @@
+#' Verify that a vector of values has the expected number of `TRUE` values
+#'
+#' @param x A logical vecotor without `NA` values
+#' @param n The expected number of `TRUE` values
+#' @returns `x` if `sum(x) == n` or an informative error message otherwise
+#' @examples
+#' data.frame(A = 1:5) %>%
+#'   dplyr::mutate(
+#'     big_values = assert_count_true(A > 2, n = 3)
+#'   )
+#' @export
+assert_count_true <- function(x, n = 1) {
+  stopifnot(is.logical(x))
+  if (any(is.na(x))) {
+    stop(deparse(substitute(x)), " has NA values")
+  }
+  if (sum(x) != n) {
+    stop_message <-
+      sprintf(
+        "`%s` expected %g `TRUE` %s but %g %s found.",
+        deparse(substitute(x)),
+        n,
+        ngettext(n, "value", "values"),
+        sum(x),
+        ngettext(sum(x), "was", "were")
+      )
+    stop(stop_message)
+  }
+  x
+}

tests/testthat/test-assert_count_true.R

@@ -0,0 +1,36 @@
+test_that("assert_count_true", {
+  expect_equal(
+    assert_count_true(TRUE, 1),
+    TRUE
+  )
+  expect_equal(
+    assert_count_true(rep(TRUE, 3), 3),
+    rep(TRUE, 3)
+  )
+  my_vector <- c(rep(TRUE, 3), FALSE)
+  expect_equal(
+    assert_count_true(my_vector, 3),
+    my_vector
+  )
+  expect_error(
+    assert_count_true(NA),
+    regexp = "NA has NA values"
+  )
+  # more informative errors
+  my_vector <- c(NA, TRUE)
+  expect_error(
+    assert_count_true(my_vector),
+    regexp = "my_vector has NA values"
+  )
+  my_vector <- c(FALSE, TRUE)
+  expect_error(
+    assert_count_true(my_vector, n = 2),
+    regexp = "`my_vector` expected 2 `TRUE` values but 1 was found."
+  )
+  # Check grammar of error message
+  my_vector <- c(TRUE, TRUE)
+  expect_error(
+    assert_count_true(my_vector, n = 1),
+    regexp = "`my_vector` expected 1 `TRUE` value but 2 were found."
+  )
+})