add tests

tests/testthat/test-method-dispatch.R

@@ -76,6 +76,28 @@ test_that("can substitute() args", {
     method(foo, class_character) <- function(x, ..., z = 1) substitute(z)
   )
   expect_equal(foo("x", z = letters), quote(letters))
+
+  suppressMessages(
+    method(foo, class_character) <- function(x, ..., z = 1) substitute(list(...))
+  )
+  expect_equal(foo("x", abc = xyz), quote(list(abc = xyz)))
+
+  suppressMessages(
+    method(foo, class_character) <- function(x, ..., z = 1, y) missing(y)
+  )
+  expect_true(foo("x"), TRUE)
+  expect_true(foo("x", y =), TRUE)
+    expect_true(foo("x", y =), TRUE)
+
+  suppressMessages(
+    method(foo, class_character) <- function(x, ..., z = 1, y) ...length()
+  )
+
+  expect_equal(foo("x"), 0)
+  expect_equal(foo("x", y =), 0)
+  expect_equal(foo("x", y =, abc), 1)
+  expect_equal(foo("x", y =, abc = xyz), 1)
+  expect_equal(foo("x", y =, abc, xyz), 2)
 })
 
 test_that("methods get values modified in the generic", {