Created rule "Writable".

This rule checks if the given data is a file exists and is writable.

README.md

@@ -286,6 +286,7 @@ Reference
   * v::file()
   * v::readable()
   * v::symbolicLink()
+  * v::writable()
 
 ### Other
 
@@ -1512,6 +1513,12 @@ See also:
   * v::digit()
   * v::alnum()
 
+#### v::writable()
+
+Validates if the given data is a file exists and is writable.
+
+    v::writable()->validate('/path/of/a/writable/file'); //true
+
 #### v::zend($zendValidator)
 
 Use Zend validators inside Respect\Validation flow. Messages

library/Respect/Validation/Exceptions/WritableException.php

@@ -0,0 +1,17 @@
+<?php
+
+namespace Respect\Validation\Exceptions;
+
+class WritableException extends ValidationException
+{
+
+    public static $defaultTemplates = array(
+        self::MODE_DEFAULT => array(
+            self::STANDARD => '{{name}} must be writable',
+        ),
+        self::MODE_NEGATIVE => array(
+            self::STANDARD => '{{name}} must not be writable',
+        )
+    );
+
+}

library/Respect/Validation/Rules/Writable.php

@@ -0,0 +1,18 @@
+<?php
+
+namespace Respect\Validation\Rules;
+
+class Writable extends AbstractRule
+{
+
+    public function validate($input)
+    {
+        if ($input instanceof \SplFileInfo) {
+            return $input->isWritable();
+        }
+
+        return (is_string($input) && is_writable($input));
+    }
+
+}
+

library/Respect/Validation/Validator.php

@@ -85,6 +85,7 @@ use Respect\Validation\Rules\AllOf;
  * @method \Respect\Validation\Validator version()
  * @method \Respect\Validation\Validator vowel()
  * @method \Respect\Validation\Validator when(Validatable $if, Validatable $then, Validatable $when)
+ * @method \Respect\Validation\Validator writable()
  * @method \Respect\Validation\Validator xdigit(string $additionalChars = null)
  * @method \Respect\Validation\Validator zend(mixed $validator, array $params = null)
  */

tests/library/Respect/Validation/Rules/WritableTest.php

@@ -0,0 +1,59 @@
+<?php
+
+namespace Respect\Validation\Rules;
+
+$GLOBALS['is_writable'] = null;
+
+function is_writable($writable)
+{
+    $return = \is_writable($writable); // Running the real function
+    if (null !== $GLOBALS['is_writable']) {
+        $return             = $GLOBALS['is_writable'];
+        $GLOBALS['is_writable'] = null;
+    }
+
+    return $return;
+}
+
+class WritableTest extends \PHPUnit_Framework_TestCase
+{
+
+    /**
+     * @covers Respect\Validation\Rules\Writable::validate
+     */
+    public function testValidWritableFileShouldReturnTrue()
+    {
+        $GLOBALS['is_writable'] = true;
+
+        $rule = new Writable();
+        $input = '/path/of/a/valid/writable/file.txt';
+        $this->assertTrue($rule->validate($input));
+    }
+
+    /**
+     * @covers Respect\Validation\Rules\Writable::validate
+     */
+    public function testInvalidWritableFileShouldReturnFalse()
+    {
+        $GLOBALS['is_writable'] = false;
+
+        $rule = new Writable();
+        $input = '/path/of/an/invalid/writable/file.txt';
+        $this->assertFalse($rule->validate($input));
+    }
+
+    /**
+     * @covers Respect\Validation\Rules\Writable::validate
+     */
+    public function testShouldValidateObjects()
+    {
+        $rule = new Writable();
+        $object = $this->getMock('SplFileInfo', array('isWritable'), array('somefile.txt'));
+        $object->expects($this->once())
+                ->method('isWritable')
+                ->will($this->returnValue(true));
+
+        $this->assertTrue($rule->validate($object));
+    }
+
+}