Make tests more compatible with TruffleRuby (#514)

* Improve encoding error test case
The test input IRB currently uses happen to hit a compatibility bug in
TruffleRuby, which has been documented in
truffleruby/truffleruby#2848
Although it'll eventually be fixed, we can make the test case support TruffleRuby
now by tweaking it just a little bit.
Co-authored-by: Kevin Menard <kevin@nirvdrum.com>
* Remove redundant TruffleRuby omits/pends
Co-authored-by: Kevin Menard <kevin@nirvdrum.com>
* Use a different way to test warning emission
The test case was added in d08ef68
to verify that IRB emits Ruby warning as expected.
But the subject it uses relies on CRuby's regexp engine, which isn't always
used in other language implementations, like TruffleRuby. That's why we
ended up skipping TruffleRuby in this test case.
Since the test isn't about regexp itself, we can change the testing subject
and just remove the special condition for TruffleRuby.
Co-authored-by: Kevin Menard <kevin@nirvdrum.com>
---------
Co-authored-by: Kevin Menard <kevin@nirvdrum.com>

Author: st0012

test/irb/test_context.rb

@@ -50,22 +50,19 @@ def test_evaluate_with_exception
 end
 
 deftest_evaluate_with_encoding_error_without_lineno
-pendifRUBY_ENGINE == 'truffleruby'
 assert_raise_with_message(EncodingError,/invalid symbol/){
-@context.evaluate(%q[{"\xAE": 1}],1)
+@context.evaluate(%q[:"\xAE"],1)
 # The backtrace of this invalid encoding hash doesn't contain lineno.
 }
 end
 
-deftest_evaluate_with_onigmo_warning
-pendifRUBY_ENGINE == 'truffleruby'
-assert_warning("(irb):1: warning: character class has duplicated range: /[aa]/\n")do
-@context.evaluate('/[aa]/',1)
+deftest_evaluate_still_emits_warning
+assert_warning("(irb):1: warning: END in method; use at_exit\n")do
+@context.evaluate(%q[def foo; END {}; end],1)
 end
 end
 
 deftest_eval_input
-pendifRUBY_ENGINE == 'truffleruby'
 verbose, $VERBOSE = $VERBOSE,nil
 input=TestInputMethod.new([
 "raise 'Foo'\n",
@@ -88,7 +85,6 @@ def test_eval_input
 end
 
 deftest_eval_input_raise2x
-pendifRUBY_ENGINE == 'truffleruby'
 input=TestInputMethod.new([
 "raise 'Foo'\n",
 "raise 'Bar'\n",
@@ -513,7 +509,6 @@ def test_eval_input_with_exception
 end
 
 deftest_eval_input_with_invalid_byte_sequence_exception
-pendifRUBY_ENGINE == 'truffleruby'
 verbose, $VERBOSE = $VERBOSE,nil
 input=TestInputMethod.new([
 %Q{def hoge() fuga; end; def fuga() raise "A\\xF3B"; end; hoge\n},