Suppress method redefinition warnings

- When running with `$VERBOSE` set to `true`, rspectre generates a very large # of warnings.

lib/rspectre/linter.rb

@@ -40,6 +40,8 @@ def self.record(node)
     def self.prepend_behavior(scope, method_name)
       original_method = scope.instance_method(method_name)
 
+      # Removing the method first prevents method redefined warnings when $VERBOSE is true
+      scope.remove_method(method_name)
       scope.__send__(:define_method, method_name) do |*args, **kwargs, &block|
         yield
 

spec/shared/highlighted_offenses.rb

@@ -64,6 +64,8 @@ def expected_offenses(source, spec_file)
 
           expect(offense.description).to eql(description)
         end
+
+        expect(stderr.empty?).to be(true), 'There was unexpected output to STDERR!'
       end
     end
   end

spec/shared/rspectre_runner.rb

@@ -12,7 +12,7 @@ def run_rspectre(source)
 
     output =
       Dir.chdir(File.dirname(spec_file.path)) do
-        Open3.capture3("#{rspectre_path} --rspec #{spec_file.path}")
+        Open3.capture3("RUBYOPT='--verbose' #{rspectre_path} --rspec #{spec_file.path}")
       end
 
     yield([output, spec_file])

spec/unused_let_spec.rb

@@ -11,7 +11,7 @@
       let(:unused_binary) { "\\xff".b }
       ^^^^^^^^^^^^^^^^^^^ UnusedLet: Unused `let` definition.
 
-      let(:unused_compound) { 1 + 1; 'noop' }
+      let(:unused_compound) { foo; 'noop' }
       ^^^^^^^^^^^^^^^^^^^^^ UnusedLet: Unused `let` definition.
 
       let(
@@ -26,7 +26,7 @@
 
       let(:unused_multiline_compound) do
       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ UnusedLet: Unused `let` definition.
-        'doop'
+        foo
         'noop'
       end