Allow unquoting first arg for expect_s4_class() (#2065)

Fixes #2064

Author: stibu81

NEWS.md

@@ -1,5 +1,6 @@
 # testthat (development version)
 
+* `expect_s4_class()` now supports unquoting (@stibu81, #2064).
 * `it()` now finds the correct evaluation environment in more cases (@averissimo, #2085).
 * Fixed an issue preventing compilation from succeeding due to deprecation / removal of `std::uncaught_exception()` (@kevinushey, #2047).
 

R/expect-inheritance.R

@@ -125,7 +125,7 @@ expect_s7_class <- function(object, class) {
 #' @rdname inheritance-expectations
 expect_s4_class <- function(object, class) {
   act <- quasi_label(enquo(object), arg = "object")
-  act_val_lab <- format_class(methods::is(object))
+  act$class <- format_class(methods::is(act$val))
   exp_lab <- format_class(class)
 
   if (identical(class, NA)) {
@@ -139,7 +139,7 @@ expect_s4_class <- function(object, class) {
     } else {
       expect(
         methods::is(act$val, class),
-        sprintf("%s inherits from %s not %s.", act$lab, act_val_lab, exp_lab)
+        sprintf("%s inherits from %s not %s.", act$lab, act$class, exp_lab)
       )
     }
   } else {

tests/testthat/test-expect-inheritance.R

@@ -62,6 +62,12 @@ test_that("expect_s3_class allows unquoting of first argument", {
 })
 
 
+test_that("expect_s4_class allows unquoting of first argument", {
+  cls <- methods::setClass("new_class", slots = c("a" = "numeric"))
+  obj <- methods::new("new_class", a = 3)
+  expect_success(expect_s4_class(!! rlang::quo(obj), "new_class"))
+})
+
 # expect_s7_class --------------------------------------------------------
 
 test_that("checks its inputs", {