Add TestProc#test_hash_equal

Author: peterzhu2118

test/ruby/test_proc.rb

@@ -159,6 +159,26 @@ def test_eq
     assert_equal(*m_nest{}, "[ruby-core:84583] Feature #14627")
   end
 
+  def test_hash_equal
+    # iseq backed proc
+    p1 = proc {}
+    p2 = p1.dup
+
+    assert_equal p1.hash, p2.hash
+
+    # ifunc backed proc
+    p1 = {}.to_proc
+    p2 = p1.dup
+
+    assert_equal p1.hash, p2.hash
+
+    # symbol backed proc
+    p1 = :hello.to_proc
+    p2 = :hello.to_proc
+
+    assert_equal p1.hash, p2.hash
+  end
+
   def test_hash_uniqueness
     def self.capture(&block)
       block