diff --git a/guides/assertion-system.rst b/guides/assertion-system.rst
new file mode 100644
index 0000000..3c3784b
--- /dev/null
+++ b/guides/assertion-system.rst
@@ -0,0 +1,367 @@
+Assertion system
+================
+
+The ``\Behat\Mink\WebAssert`` class provides a set of assertions. There are assertions
+about the address of the page, the cookies, the status code, the response headers,
+the content of the page, the page elements...
+
+.. note::
+
+    If an assertion evaluates to false, an exception ``Behat\Mink\Exception\ExpectationException``
+    is thrown.
+
+Mink initialisation
+-------------------
+
+.. code-block:: php
+
+    // Choose a Mink driver.
+    $driver = new \Behat\Mink\Driver\GoutteDriver();
+    $session = new \Behat\Mink\Session($driver);
+    $mink = new \Behat\Mink\Mink(array('goutte' => $session));
+    $mink->setDefaultSessionName('goutte');
+
+Checking address
+----------------
+
+``WebAssert::addressEquals``
+    Checks that current session address is equals to provided one.
+
+``WebAssert::addressNotEquals``
+    Checks that current session address is not equals to provided one.
+
+.. code-block:: php
+
+    $mink->getSession()->visit('http://exemple.com');
+
+    $mink->assertSession()->addressEquals('http://example.com/');
+    $mink->assertSession()->addressEquals('/');
+
+    $mink->assertSession()->addressNotEquals('http://example.com/not_found');
+    $mink->assertSession()->addressNotEquals('/not_found');
+
+``WebAssert::addressMatches``
+    Checks that current session address matches regex.
+
+.. code-block:: php
+
+    $mink->getSession()->visit('http://example.com/script.php/sub/url/foo/bar');
+
+    $mink->assertSession()->addressMatches('/sub.*bar/');
+
+.. caution::
+  Webassert compare only the path and the fragment (after the hashmark #). The scheme,
+  the host, the query (after the question mark ?) are not taken into account.
+
+  These examples didn't throw exception:
+
+  .. code-block:: php
+
+    $mink->getSession()->visit('http://example.com');
+    // different scheme
+    $mink->assertSession()->addressEquals('https://example.com');
+    // different host
+    $mink->assertSession()->addressEquals('https://another.com');
+
+
+    $mink->getSession()->visit('http://example.com/script.php/sub/url?param=true#webapp/nav');
+    // Without query string
+    $mink->assertSession()->addressEquals('http://examyyyyyple.com/sub/url#webapp/nav');
+
+Checking cookie
+---------------
+
+``WebAssert::cookieExists``
+    Checks that specified cookie exists.
+
+``WebAssert::cookieEquals``
+    Checks that specified cookie exists and its value.
+
+.. code-block:: php
+
+    $mink->assertSession()->cookieExists('cookie_name');
+    $mink->assertSession()->cookieEquals('cookie_name', 'foo_value');
+
+Checking status code
+--------------------
+
+``WebAssert::statusCodeEquals``
+    Checks that current response code equals to provided one.
+
+``WebAssert::statusCodeNotEquals``
+    Checks that current response code not equals to provided one.
+
+.. code-block:: php
+
+    $mink->assertSession()->statusCodeEquals(200);
+    $mink->assertSession()->statusCodeNotEquals(500);
+
+.. note::
+
+    See the :ref:`driver-feature-support` to see which driver supports this feature.
+
+Checking response headers
+-------------------------
+
+``WebAssert::responseHeaderEquals``
+    Checks that current response header equals value.
+
+``WebAssert::responseHeaderNotEquals``
+    Checks that current response header does not equal value.
+
+``WebAssert::responseHeaderContains``
+    Checks that current response header contains value.
+
+``WebAssert::responseHeaderNotContains``
+    Checks that current response header does not contain value.
+
+.. code-block:: php
+
+    $mink->assertSession()->responseHeaderEquals('Content-Type', 'text/html;charset=utf-8');
+    $mink->assertSession()->responseHeaderNotEquals('Content-Type', 'application/json');
+    $mink->assertSession()->responseHeaderContains('Content-Type', 'charset=utf-8');
+    $mink->assertSession()->responseHeaderNotContains('Content-Type', 'application/json');
+
+``WebAssert::responseHeaderMatches``
+    Checks that current response header matches regex.
+
+``WebAssert::responseHeaderNotMatches``
+    Checks that current response header does not match regex.
+
+.. code-block:: php
+
+    $mink->assertSession()->responseHeaderMatches('Content-Type', '/text.*charset.*/');
+    $mink->assertSession()->responseHeaderNotMatches('Content-Type', '/application.*charset.*/');
+
+.. note::
+
+    See the :ref:`driver-feature-support` to see which driver supports this feature.
+
+Checking response text content
+------------------------------
+
+WebAssert can checks the text content of current page. The comparison is case-insensitive.
+
+``WebAssert::pageTextContains``
+    Checks that current page contains text.
+
+``WebAssert::pageTextNotContains``
+    Checks that current page does not contains text.
+
+.. code-block:: php
+
+    $mink->assertSession()->pageTextContains('Example');
+    $mink->assertSession()->pageTextNotContains('Examplefoobar');
+
+``WebAssert::pageTextMatches``
+    Checks that current page text matches regex.
+
+``WebAssert::pageTextNotMatches``
+    Checks that current page text does not matches regex.
+
+.. code-block:: php
+
+    $mink->assertSession()->pageTextMatches('/Example/');
+    $mink->assertSession()->pageTextNotMatches('/Examplefoobar/');
+
+Checking response HTML content
+------------------------------
+
+WebAssert can checks the HTML content of current page. The comparison is case-insensitive.
+
+``WebAssert::responseContains``
+    Checks that page HTML (response content) contains text.
+
+``WebAssert::responseNotContains``
+    Checks that page HTML (response content) does not contains text.
+
+.. code-block:: php
+
+    $mink->assertSession()->responseContains('<h1>Example Domain</h1>');
+    $mink->assertSession()->responseNotContains('<h2>Example Domain </h2>');
+
+``WebAssert::responseMatches``
+    Checks that page HTML (response content) matches regex.
+
+``WebAssert::responseNotMatches``
+    Checks that page HTML (response content) does not matches regex.
+
+.. code-block:: php
+
+    $mink->assertSession()->responseMatches('/<h1>Example.*<\/h1>/');
+    $mink->assertSession()->responseNotMatches('/<h1>ExampleFooBar.*<\/h1>/');
+
+Checking elements
+-----------------
+
+``WebAssert::element*`` supports same :ref:`selectors <selectors>` that the
+``ElementInterface::find`` and ``ElementInterface::findAll`` methods.
+
+``WebAssert::elementsCount``
+    Checks that there is specified number of specific elements on the page.
+
+.. code-block:: php
+
+    $mink->assertSession()->elementsCount('css', 'h1', 1);
+
+``WebAssert::elementExists``
+    Checks that specific element exists on the current page.
+
+.. code-block:: php
+
+    $titleNodeElement = $mink->assertSession()->elementExists('css', 'h1');
+
+``WebAssert::elementNotExists``
+    Checks that specific element does not exists on the current page.
+
+.. code-block:: php
+
+    $mink->assertSession()->elementNotExists('css', 'h5');
+
+``WebAssert::elementTextContains``
+    Checks that specific element contains text. The comparison is case-insensitive.
+
+.. code-block:: php
+
+    $mink->assertSession()->elementTextContains('css', 'h1', 'Example Domain');
+
+``WebAssert::elementTextNotContains``
+    Checks that specific element does not contains text. The comparison is case-insensitive.
+
+.. code-block:: php
+
+    $mink->assertSession()->elementTextNotContains('css', 'h1', 'ExampleFooBar');
+
+``WebAssert::elementContains``
+    Checks that specific element contains HTML. The comparison is case-insensitive.
+
+.. code-block:: php
+
+    $mink->assertSession()->elementContains('css', 'div', '<h1>Example Domain</h1>');
+
+``WebAssert::elementNotContains``
+    Checks that specific element does not contains HTML. The comparison is case-insensitive.
+
+.. code-block:: php
+
+    $mink->assertSession()->elementNotContains('css', 'div', '<h1>ExampleFooBar</h1>');
+
+``Webassert::elementAttributeExists``
+    Checks that an attribute exists in an element.
+
+.. code-block:: php
+
+    $mink->assertSession()->elementAttributeExists('css', 'a', 'href');
+
+``Webassert::elementAttributeContains``
+    Checks that an attribute of a specific elements contains text. The comparison is case-insensitive.
+
+.. code-block:: php
+
+    $mink->assertSession()->elementAttributeContains('css', 'a', 'href', 'http://');
+
+``Webassert::elementAttributeNotContains``
+    Checks that an attribute of a specific elements does not contain text.
+
+.. code-block:: php
+
+    $mink->assertSession()->elementAttributeNotContains('css', 'a', 'href', 'https://');
+
+All ``Webassert::field*`` use the :ref:`field named selector <named-selector>`.
+
+``Webassert::fieldExists``
+    Checks that specific field exists on the current page.
+
+.. code-block:: php
+
+    $mink->assertSession()->fieldExists('username');
+
+``Webassert::fieldNotExists``
+    Checks that specific field does not exists on the current page.
+
+.. code-block:: php
+
+    $mink->assertSession()->fieldNotExists('not_exists');
+
+``Webassert::fieldValueEquals``
+    Checks that specific field have provided value. The comparison is case-insensitive.
+
+.. code-block:: php
+
+    $mink->assertSession()->fieldValueEquals('username', 'foo');
+
+``Webassert::fieldValueNotEquals``
+    Checks that specific field have provided value. The comparison is case-insensitive.
+
+.. code-block:: php
+
+    $mink->assertSession()->fieldValueEquals('username', 'foo');
+
+All ``Webassert::checkbox*`` use the :ref:`checkbox named selector <named-selector>`.
+
+``Webassert::checkboxChecked``
+    Checks that specific checkbox is checked.
+
+.. code-block:: php
+
+    $mink->assertSession()->checkboxChecked('remember_me');
+
+``Webassert::checkboxNotChecked``
+    Checks that specific checkbox is unchecked.
+
+.. code-block:: php
+
+    $mink->assertSession()->checkboxNotChecked('remember_me');
+
+Nested Traversing
+-----------------
+
+Every ``WebAssert::*Exists`` method return a ``Behat\Mink\Element\NodeElement``
+(Except of course ``WebAssert::*NotExists`` methods).
+
+``WebAssert::elementsCount``, ``WebAssert::elementExists``, ``WebAssert::elementNotExists``,
+``Webassert::field*``, ``Webassert::checkbox*``methods support an ``ElementInterface``
+argument in order to not search on all the page but only in an element of the page.
+
+So, instead of that:
+
+.. code-block:: php
+
+    $registerForm = $page->find('css', 'form.register');
+
+    if (null === $registerForm) {
+        throw new \Exception('The element is not found');
+    }
+
+    $field = $registerForm->findField('Email');
+
+    if (null === $field) {
+        throw new \Exception('The element is not found');
+    }
+
+    $field->setValue('foo@example.com');
+
+you can do:
+
+.. code-block:: php
+
+    // Throw exception when not found instead of returning null.
+    $registerForm = $mink->assertSession()->elementExists('css', 'form.register');
+
+    $field = $mink->assertSession()->fieldExists('Email', $registerForm);
+
+    $field->setValue('foo@example.com');
+
+This can improve code readability or avoid having a fatal error in method chaining.
+
+Webassert and multisessions
+---------------------------
+
+You could use an another session by calling ``assertSession`` with a session name
+or an instance of ``\Behat\Mink\Session``.
+
+.. code-block:: php
+
+    $mink->assertSession()->elementExists('css', 'form.register');
+    $mink->assertSession('goutte')->elementExists('css', 'form.register');
+    $mink->assertSession($mink->getSession('goutte'))->elementExists('css', 'form.register');
diff --git a/index.rst b/index.rst
index 57b6351..6c084d2 100644
--- a/index.rst
+++ b/index.rst
@@ -74,6 +74,7 @@ Learn Mink with the topical guides:
     guides/interacting-with-pages
     guides/drivers
     guides/managing-sessions
+    guides/assertion-system
     contributing
 
 Testing Tools Integration