Add tests for invalid ranges

test/integration/expression_test.rb

@@ -29,6 +29,12 @@ class ExpressionTest < Minitest::Test
   def test_range
     assert_equal(1..2, parse_and_eval("(1..2)"))
     assert_equal(3..4, parse_and_eval(" ( 3 .. 4 ) "))
+    assert_equal(0..0, parse_and_eval("('a'..'b')"))
+
+    with_error_mode(:strict) do
+      e = assert_raises(NoMethodError) { parse_and_eval("(1..(1..5))") }
+      assert_match(/undefined method `to_i' for 1..5:Range/, e.message)
+    end
   end
 
   private