Objects with __toString() can be asserted.

In a recent change, some regex matches changed to stripos() calls.
The problem is that stripos() converts the needle parameter to int
if it is not a string. While objects having __toString() can be
converted into string by most of the internal PHP functions, they
cannot be converted to int, resulting in an error.

src/WebAssert.php

@@ -190,7 +190,7 @@ public function responseHeaderContains($name, $value)
         $actual = $this->session->getResponseHeader($name);
         $message = sprintf('The text "%s" was not found anywhere in the "%s" response header.', $value, $name);
 
-        $this->assert(false !== stripos($actual, $value), $message);
+        $this->assert(false !== stripos($actual, (string) $value), $message);
     }
 
     /**
@@ -206,7 +206,7 @@ public function responseHeaderNotContains($name, $value)
         $actual = $this->session->getResponseHeader($name);
         $message = sprintf('The text "%s" was found in the "%s" response header, but it should not.', $value, $name);
 
-        $this->assert(false === stripos($actual, $value), $message);
+        $this->assert(false === stripos($actual, (string) $value), $message);
     }
 
     /**
@@ -321,7 +321,7 @@ public function responseContains($text)
         $actual = $this->session->getPage()->getContent();
         $message = sprintf('The string "%s" was not found anywhere in the HTML response of the current page.', $text);
 
-        $this->assert(stripos($actual, $text) !== false, $message);
+        $this->assert(stripos($actual, (string) $text) !== false, $message);
     }
 
     /**
@@ -336,7 +336,7 @@ public function responseNotContains($text)
         $actual = $this->session->getPage()->getContent();
         $message = sprintf('The string "%s" appears in the HTML response of this page, but it should not.', $text);
 
-        $this->assert(stripos($actual, $text) === false, $message);
+        $this->assert(stripos($actual, (string) $text) === false, $message);
     }
 
     /**

tests/WebAssertTest.php

@@ -3,6 +3,7 @@
 namespace Behat\Mink\Tests;
 
 use Behat\Mink\Exception\ExpectationException;
+use Behat\Mink\Tests\helpers\Stringer;
 use Behat\Mink\WebAssert;
 use PHPUnit\Framework\TestCase;
 
@@ -255,7 +256,7 @@ public function testResponseHeaderContains()
                 )
             ));
 
-        $this->assertCorrectAssertion('responseHeaderContains', array('foo', 'ba'));
+        $this->assertCorrectAssertion('responseHeaderContains', array('foo', new Stringer('ba')));
         $this->assertWrongAssertion(
             'responseHeaderContains',
             array('bar', 'bz'),
@@ -276,7 +277,7 @@ public function testResponseHeaderNotContains()
                 )
             ));
 
-        $this->assertCorrectAssertion('responseHeaderNotContains', array('foo', 'bz'));
+        $this->assertCorrectAssertion('responseHeaderNotContains', array('foo', new Stringer('bz')));
         $this->assertWrongAssertion(
             'responseHeaderNotContains',
             array('bar', 'ba'),
@@ -458,7 +459,7 @@ public function testResponseContains()
             ->will($this->returnValue('Some page text'))
         ;
 
-        $this->assertCorrectAssertion('responseContains', array('PAGE text'));
+        $this->assertCorrectAssertion('responseContains', array(new Stringer('PAGE text')));
         $this->assertWrongAssertion(
             'responseContains',
             array('html text'),
@@ -486,7 +487,7 @@ public function testResponseNotContains()
             ->will($this->returnValue('Some html text'))
         ;
 
-        $this->assertCorrectAssertion('responseNotContains', array('PAGE text'));
+        $this->assertCorrectAssertion('responseNotContains', array(new Stringer('PAGE text')));
         $this->assertWrongAssertion(
             'responseNotContains',
             array('HTML text'),

tests/helpers/Stringer.php

@@ -0,0 +1,42 @@
+<?php
+
+namespace Behat\Mink\Tests\helpers;
+
+/**
+ * Class Stringer
+ *
+ * A container class to hold a string.
+ *
+ * @package Behat\Mink\Tests\helpers
+ */
+class Stringer
+{
+
+  /**
+   * Internal storage.
+   *
+   * @var string
+   */
+  protected $content;
+
+  /**
+   * Stringer constructor.
+   *
+   * @param $content
+   */
+  public function __construct($content)
+  {
+    $this->content = $content;
+  }
+
+  /**
+   * Returns in the wrapped string.
+   *
+   * @return string
+   */
+  public function __toString()
+  {
+    return $this->content;
+  }
+
+}