Check if actual checkbox value equals checkedValue

Author: jrauh01

src/FormElement/CheckboxElement.php

@@ -121,4 +121,28 @@ public function renderUnwrapped()
 
         return (new HiddenElement($this->getValueOfNameAttribute(), ['value' => $this->getUncheckedValue()])) . $html;
     }
+
+    /**
+     * Validate the element using all registered validators
+     *
+     * @return $this
+     */
+    public function validate()
+    {
+        $this->ensureAssembled();
+
+        if (! $this->hasValue() || $this->getValue() !== $this->getCheckedValue()) {
+            if ($this->isRequired()) {
+                $this->setMessages([$this->translate('This field is required.')]);
+                $this->valid = false;
+            } else {
+                $this->valid = true;
+            }
+        } else {
+            $this->valid = $this->getValidators()->isValid($this->getValue());
+            $this->setMessages($this->getValidators()->getMessages());
+        }
+
+        return $this;
+    }
 }