Add tests for multi-statement evaluate_script via IIFE

README.md

@@ -611,13 +611,23 @@ In drivers which support it, you can easily execute JavaScript:
 page.execute_script("$('body').empty()")
 ```
 
-For simple expressions, you can return the result of the script. Note
-that this may break with more complicated expressions:
+For simple expressions, you can return the result of the script.
 
 ```ruby
 result = page.evaluate_script('4 + 4');
 ```
 
+For more complicated scripts you'll need to write them as one expression.
+
+```ruby
+result = page.evaluate_script(<<~JS, 3, element)
+  (function(n, el){
+    var val = parseInt(el.value, 10);
+    return n+val;
+  })(arguments[0], arguments[1])
+JS
+```
+
 ### <a name="modals"></a>Modals
 
 In drivers which support it, you can accept, dismiss and respond to alerts, confirms and prompts.

lib/capybara/spec/session/evaluate_script_spec.rb

@@ -34,4 +34,16 @@ Capybara::SpecHelper.spec '#evaluate_script', requires: [:js] do
     expect(el).to be_instance_of(Capybara::Node::Element)
     expect(el).to eq(@session.find(:css, '#change'))
   end
+
+  it 'should support multi statement via IIFE' do
+    @session.visit('/with_js')
+    @session.find(:css, '#change')
+    el = @session.evaluate_script(<<~JS)
+      (function(){
+        var el = document.getElementById('change');
+        return el;
+      })()
+    JS
+    expect(el).to eq(@session.find(:css, '#change'))
+  end
 end

lib/capybara/spec/session/node_spec.rb

@@ -774,6 +774,18 @@ Capybara::SpecHelper.spec 'node' do
       expect(el).to be_instance_of(Capybara::Node::Element)
       expect(el).to eq(change)
     end
+
+    it 'should support multiple statements via IIFE' do
+      @session.visit('/with_js')
+      change = @session.find(:css, '#change') # ensure page has loaded and element is available
+      res = change.evaluate_script(<<~JS, 3)
+        (function(n){
+          var el = this;
+          return [el, n];
+        }).apply(this, arguments)
+      JS
+      expect(res).to eq [change, 3]
+    end
   end
 
   describe '#evaluate_async_script', requires: %i[js es_args] do