Check expect() inputs

Fixes #2247

Author: hadley

R/expectation.R

@@ -20,6 +20,9 @@ expect <- function(
   trace = NULL,
   trace_env = caller_env()
 ) {
+  check_bool(ok)
+  check_character(failure_message)
+
   if (!ok) {
     return(fail(
       failure_message,

tests/testthat/_snaps/expectation.md

@@ -0,0 +1,13 @@
+# validates key inputs
+
+    Code
+      expect(1)
+    Condition
+      Error in `expect()`:
+      ! `ok` must be `TRUE` or `FALSE`, not the number 1.
+    Code
+      expect(TRUE, 1)
+    Condition
+      Error in `expect()`:
+      ! `failure_message` must be a character vector, not the number 1.
+

tests/testthat/test-expectation.R

@@ -7,6 +7,13 @@ test_that("info only evaluated on failure", {
   expect_no_error(expect(TRUE, "fail", info = stop("!")))
 })
 
+test_that("validates key inputs", {
+  expect_snapshot(error = TRUE, {
+    expect(1)
+    expect(TRUE, 1)
+  })
+})
+
 test_that("can subclass expectation", {
   exp <- new_expectation(
     "failure",