Use dedicated assertion methods for warning and syntax error

test/ruby/test_parse.rb

@@ -855,32 +855,24 @@ x = __ENCODING__
   end
 
   def test_void_expr_stmts_value
-    # This test checks if void contexts are warned correctly.
-    # Thus, warnings MUST NOT be suppressed.
-    $VERBOSE = true
-    stderr = $stderr
-    $stderr = StringIO.new("")
     x = 1
-    assert_nil eval("x; nil")
-    assert_nil eval("1+1; nil")
-    assert_nil eval("1.+(1); nil")
-    assert_nil eval("TestParse; nil")
-    assert_nil eval("::TestParse; nil")
-    assert_nil eval("x..x; nil")
-    assert_nil eval("x...x; nil")
-    assert_nil eval("self; nil")
-    assert_nil eval("nil; nil")
-    assert_nil eval("true; nil")
-    assert_nil eval("false; nil")
-    assert_nil eval("defined?(1); nil")
+    useless_use = /useless use/
+    unused = /unused/
+    assert_nil assert_warning(useless_use) {eval("x; nil")}
+    assert_nil assert_warning(useless_use) {eval("1+1; nil")}
+    assert_nil assert_warning('') {eval("1.+(1); nil")}
+    assert_nil assert_warning(useless_use) {eval("TestParse; nil")}
+    assert_nil assert_warning(useless_use) {eval("::TestParse; nil")}
+    assert_nil assert_warning(useless_use) {eval("x..x; nil")}
+    assert_nil assert_warning(useless_use) {eval("x...x; nil")}
+    assert_nil assert_warning(unused) {eval("self; nil")}
+    assert_nil assert_warning(unused) {eval("nil; nil")}
+    assert_nil assert_warning(unused) {eval("true; nil")}
+    assert_nil assert_warning(unused) {eval("false; nil")}
+    assert_nil assert_warning(useless_use) {eval("defined?(1); nil")}
     assert_equal 1, x
 
-    assert_raise(SyntaxError) do
-      eval %q(1; next; 2)
-    end
-
-    assert_equal(13, $stderr.string.lines.to_a.size)
-    $stderr = stderr
+    assert_syntax_error("1; next; 2", /Invalid next/)
   end
 
   def test_assign_in_conditional