1 files changed, 93 insertions, 0 deletions
diff --git a/test/prism/parameters_signature_test.rb b/test/prism/parameters_signature_test.rb
new file mode 100644
index 0000000000..0eed8d993d
--- /dev/null
+++ b/test/prism/parameters_signature_test.rb
@@ -0,0 +1,93 @@
+# frozen_string_literal: true
+
+require_relative "test_helper"
+
+return if RUBY_VERSION < "3.2"
+
+module Prism
+  class ParametersSignatureTest < TestCase
+    def test_req
+      assert_parameters([[:req, :a]], "a")
+    end
+
+    def test_req_destructure
+      assert_parameters([[:req]], "(a, b)")
+    end
+
+    def test_opt
+      assert_parameters([[:opt, :a]], "a = 1")
+    end
+
+    def test_rest
+      assert_parameters([[:rest, :a]], "*a")
+    end
+
+    def test_rest_anonymous
+      assert_parameters([[:rest, :*]], "*")
+    end
+
+    def test_post
+      assert_parameters([[:rest, :a], [:req, :b]], "*a, b")
+    end
+
+    def test_post_destructure
+      assert_parameters([[:rest, :a], [:req]], "*a, (b, c)")
+    end
+
+    def test_keyreq
+      assert_parameters([[:keyreq, :a]], "a:")
+    end
+
+    def test_key
+      assert_parameters([[:key, :a]], "a: 1")
+    end
+
+    def test_keyrest
+      assert_parameters([[:keyrest, :a]], "**a")
+    end
+
+    def test_nokey
+      assert_parameters([[:nokey]], "**nil")
+    end
+
+    def test_keyrest_anonymous
+      assert_parameters([[:keyrest, :**]], "**")
+    end
+
+    def test_key_ordering
+      omit("TruffleRuby returns keys in order they were declared") if RUBY_ENGINE == "truffleruby"
+
+      assert_parameters([[:keyreq, :a], [:keyreq, :b], [:key, :c], [:key, :d]], "a:, c: 1, b:, d: 2")
+    end
+
+    def test_block
+      assert_parameters([[:block, :a]], "&a")
+    end
+
+    def test_block_anonymous
+      assert_parameters([[:block, :&]], "&")
+    end
+
+    def test_forwarding
+      assert_parameters([[:rest, :*], [:keyrest, :**], [:block, :&]], "...")
+    end
+
+    private
+
+    def assert_parameters(expected, source)
+      eval("def self.m(#{source}); end")
+
+      begin
+        assert_equal(expected, method(:m).parameters)
+        assert_equal(expected, signature(source))
+      ensure
+        singleton_class.undef_method(:m)
+      end
+    end
+
+    def signature(source)
+      program = Prism.parse("def m(#{source}); end").value
+      program.statements.body.first.parameters.signature
+    end
+  end
+end