diff --git a/src/TwigExtension.php b/src/TwigExtension.php
index 9bd311d..14fed21 100644
--- a/src/TwigExtension.php
+++ b/src/TwigExtension.php
@@ -237,7 +237,7 @@ class TwigExtension extends \Twig_Extension {
    *   The new text if matches are found, otherwise unchanged text.
    */
   public function pregReplaceFilter($text, $pattern, $replacement) {
-    return preg_replace('/' . preg_quote($pattern, '/') . '/', $replacement, $text);
+    return preg_replace("/$pattern/", $replacement, $text);
   }
 
   /**
diff --git a/tests/src/Functional/TwigTweakTest.php b/tests/src/Functional/TwigTweakTest.php
new file mode 100644
index 0000000..b47af1a
--- /dev/null
+++ b/tests/src/Functional/TwigTweakTest.php
@@ -0,0 +1,124 @@
+<?php
+
+namespace Drupal\Tests\twig_tweak\Functional;
+
+use Drupal\Tests\BrowserTestBase;
+
+/**
+ * Tests twig_tweak twig extension.
+ *
+ * @group twig_tweak
+ */
+class TwigTweakTest extends BrowserTestBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public static $modules = [
+    'twig_tweak',
+    'twig_tweak_test',
+    'views',
+    'node',
+    'block',
+    'image',
+  ];
+
+  /**
+   * {@inheritdoc}
+   */
+  public function setUp() {
+    parent::setUp();
+    $this->createContentType(['type' => 'page']);
+    $this->createNode(['title' => 'Alpha']);
+    $this->createNode(['title' => 'Beta']);
+    $this->createNode(['title' => 'Gamma']);
+  }
+
+  /**
+   * Tests output produced by the twig extension.
+   */
+  public function testOutput() {
+    $this->drupalGet('<front>');
+
+    // Test default views display.
+    $xpath = '//div[@class = "tt-view-default"]';
+    $xpath .= '//div[contains(@class, "view-twig-tweak-test") and contains(@class, "view-display-id-default")]';
+    $xpath .= '/div[@class = "view-content"]//ul[count(./li) = 3]/li';
+    $this->assertByXpath($xpath . '//a[contains(@href, "/node/1") and . = "Alpha"]');
+    $this->assertByXpath($xpath . '//a[contains(@href, "/node/2") and . = "Beta"]');
+    $this->assertByXpath($xpath . '//a[contains(@href, "/node/3") and . = "Gamma"]');
+
+    // Test page_1 view display.
+    $xpath = '//div[@class = "tt-view-page_1"]';
+    $xpath .= '//div[contains(@class, "view-twig-tweak-test") and contains(@class, "view-display-id-page_1")]';
+    $xpath .= '/div[@class = "view-content"]//ul[count(./li) = 3]/li';
+    $this->assertByXpath($xpath . '//a[contains(@href, "/node/1") and . = "Alpha"]');
+    $this->assertByXpath($xpath . '//a[contains(@href, "/node/2") and . = "Beta"]');
+    $this->assertByXpath($xpath . '//a[contains(@href, "/node/3") and . = "Gamma"]');
+
+    // Test view argument.
+    $xpath = '//div[@class = "tt-view-page_1-with-argument"]';
+    $xpath .= '//div[contains(@class, "view-twig-tweak-test")]';
+    $xpath .= '/div[@class = "view-content"]//ul[count(./li) = 1]/li';
+    $this->assertByXpath($xpath . '//a[contains(@href, "/node/1") and . = "Alpha"]');
+
+    // Test entity default view mode.
+    $xpath = '//div[@class = "tt-entity-default"]';
+    $xpath .= '/article[contains(@class, "node") and not(contains(@class, "node--view-mode-teaser"))]';
+    $xpath .= '/h2/a/span[. = "Alpha"]';
+    $this->assertByXpath($xpath);
+
+    // Test entity teaser view mode.
+    $xpath = '//div[@class = "tt-entity-teaser"]';
+    $xpath .= '/article[contains(@class, "node") and contains(@class, "node--view-mode-teaser")]';
+    $xpath .= '/h2/a/span[. = "Alpha"]';
+    $this->assertByXpath($xpath);
+
+    // Test loading entity from url.
+    $xpath = '//div[@class = "tt-entity-from-url" and . = ""]';
+    $this->assertByXpath($xpath);
+
+    $this->drupalGet('/node/2');
+    $xpath = '//div[@class = "tt-entity-from-url"]';
+    $xpath .= '/article[contains(@class, "node")]';
+    $xpath .= '/h2/a/span[. = "Beta"]';
+    $this->assertByXpath($xpath);
+
+    // Test field.
+    $xpath = '//div[@class = "tt-field"]/div[contains(@class, "field--name-body")]/p[. != ""]';
+    $this->assertByXpath($xpath);
+
+    // Test block.
+    $xpath = '//div[@class = "tt-block"]';
+    $xpath .= '/div[@id="block-powered-by-drupal"]/span[contains(., "Powered by Drupal")]';
+    $this->assertByXpath($xpath);
+
+    // Test token.
+    $xpath = '//div[@class = "tt-token" and . = "Drupal"]';
+    $this->assertByXpath($xpath);
+
+    // Test config.
+    $xpath = '//div[@class = "tt-config" and . = "Anonymous"]';
+    $this->assertByXpath($xpath);
+
+    // Test token replacement.
+    $xpath = '//div[@class = "tt-token-replace" and . = "Site name: Drupal"]';
+    $this->assertByXpath($xpath);
+
+    // Test preg replacement.
+    $xpath = '//div[@class = "tt-preg-replace" and . = "foo-bar"]';
+    $this->assertByXpath($xpath);
+
+    // Test image style.
+    $xpath = '//div[@class = "tt-image-style" and contains(., "styles/thumbnail/public/images/ocean.jpg")]';
+    $this->assertByXpath($xpath);
+  }
+
+  /**
+   * Checks that an element specified by a the xpath exists on the current page.
+   */
+  public function assertByXpath($xpath) {
+    $this->assertSession()->elementExists('xpath', $xpath);
+  }
+
+}
diff --git a/tests/twig_tweak_test/config/install/block.block.powered_by_drupal.yml b/tests/twig_tweak_test/config/install/block.block.powered_by_drupal.yml
new file mode 100644
index 0000000..59a2f51
--- /dev/null
+++ b/tests/twig_tweak_test/config/install/block.block.powered_by_drupal.yml
@@ -0,0 +1,16 @@
+langcode: en
+status: true
+dependencies:
+  module:
+    - system
+id: powered_by_drupal
+region: main
+weight: 10
+provider: null
+plugin: system_powered_by_block
+settings:
+  id: system_powered_by_block
+  label: 'Powered by Drupal'
+  provider: system
+  label_display: '0'
+visibility: {  }
diff --git a/tests/twig_tweak_test/config/install/views.view.twig_tweak_test.yml b/tests/twig_tweak_test/config/install/views.view.twig_tweak_test.yml
new file mode 100644
index 0000000..959fb25
--- /dev/null
+++ b/tests/twig_tweak_test/config/install/views.view.twig_tweak_test.yml
@@ -0,0 +1,193 @@
+langcode: en
+status: true
+dependencies:
+  module:
+    - node
+    - user
+id: twig_tweak_test
+label: 'Twig tweak test'
+module: views
+description: ''
+tag: ''
+base_table: node_field_data
+base_field: nid
+core: 8.x
+display:
+  default:
+    display_plugin: default
+    id: default
+    display_title: Master
+    position: 0
+    display_options:
+      access:
+        type: perm
+        options:
+          perm: 'access content'
+      cache:
+        type: tag
+        options: {  }
+      query:
+        type: views_query
+        options:
+          disable_sql_rewrite: false
+          distinct: false
+          replica: false
+          query_comment: ''
+          query_tags: {  }
+      exposed_form:
+        type: basic
+        options:
+          submit_button: Apply
+          reset_button: false
+          reset_button_label: Reset
+          exposed_sorts_label: 'Sort by'
+          expose_sort_order: true
+          sort_asc_label: Asc
+          sort_desc_label: Desc
+      pager:
+        type: none
+        options:
+          offset: 0
+      style:
+        type: html_list
+      row:
+        type: fields
+        options:
+          default_field_elements: true
+          inline: {  }
+          separator: ''
+          hide_empty: false
+      fields:
+        title:
+          id: title
+          table: node_field_data
+          field: title
+          entity_type: node
+          entity_field: title
+          label: ''
+          alter:
+            alter_text: false
+            make_link: false
+            absolute: false
+            trim: false
+            word_boundary: false
+            ellipsis: false
+            strip_tags: false
+            html: false
+          hide_empty: false
+          empty_zero: false
+          settings:
+            link_to_entity: true
+          plugin_id: field
+          relationship: none
+          group_type: group
+          admin_label: ''
+          exclude: false
+          element_type: ''
+          element_class: ''
+          element_label_type: ''
+          element_label_class: ''
+          element_label_colon: true
+          element_wrapper_type: ''
+          element_wrapper_class: ''
+          element_default_classes: true
+          empty: ''
+          hide_alter_empty: true
+          click_sort_column: value
+          type: string
+          group_column: value
+          group_columns: {  }
+          group_rows: true
+          delta_limit: 0
+          delta_offset: 0
+          delta_reversed: false
+          delta_first_last: false
+          multi_type: separator
+          separator: ', '
+          field_api_classes: false
+      filters: {  }
+      sorts:
+        nid:
+          id: nid
+          table: node_field_data
+          field: nid
+          relationship: none
+          group_type: group
+          admin_label: ''
+          order: ASC
+          exposed: false
+          expose:
+            label: ''
+          entity_type: node
+          entity_field: nid
+          plugin_id: standard
+      title: 'Twig tweak test'
+      header: {  }
+      footer: {  }
+      empty: {  }
+      relationships: {  }
+      arguments:
+        nid:
+          id: nid
+          table: node_field_data
+          field: nid
+          relationship: none
+          group_type: group
+          admin_label: ''
+          default_action: ignore
+          exception:
+            value: all
+            title_enable: false
+            title: All
+          title_enable: false
+          title: ''
+          default_argument_type: fixed
+          default_argument_options:
+            argument: ''
+          default_argument_skip_url: false
+          summary_options:
+            base_path: ''
+            count: true
+            items_per_page: 25
+            override: false
+          summary:
+            sort_order: asc
+            number_of_records: 0
+            format: default_summary
+          specify_validation: false
+          validate:
+            type: none
+            fail: 'not found'
+          validate_options: {  }
+          break_phrase: false
+          not: false
+          entity_type: node
+          entity_field: nid
+          plugin_id: node_nid
+      display_extenders: {  }
+    cache_metadata:
+      max-age: -1
+      contexts:
+        - 'languages:language_content'
+        - 'languages:language_interface'
+        - url
+        - 'user.node_grants:view'
+        - user.permissions
+      tags: {  }
+  page_1:
+    display_plugin: page
+    id: page_1
+    display_title: Page
+    position: 1
+    display_options:
+      display_extenders: {  }
+      path: twig-tweak-test
+    cache_metadata:
+      max-age: -1
+      contexts:
+        - 'languages:language_content'
+        - 'languages:language_interface'
+        - url
+        - 'user.node_grants:view'
+        - user.permissions
+      tags: {  }
diff --git a/tests/twig_tweak_test/templates/twig-tweak-test.html.twig b/tests/twig_tweak_test/templates/twig-tweak-test.html.twig
new file mode 100644
index 0000000..2cbaa19
--- /dev/null
+++ b/tests/twig_tweak_test/templates/twig-tweak-test.html.twig
@@ -0,0 +1,15 @@
+<div class="tt-test" style="background-color: lavender">
+  <div class="tt-view-default">{{ drupal_view('twig_tweak_test') }}</div>
+  <div class="tt-view-page_1">{{ drupal_view('twig_tweak_test', 'page_1') }}</div>
+  <div class="tt-view-page_1-with-argument">{{ drupal_view('twig_tweak_test', 'page_1', 1) }}</div>
+  <div class="tt-entity-default">{{ drupal_entity('node', 1) }}</div>
+  <div class="tt-entity-teaser">{{ drupal_entity('node', 1, 'teaser') }}</div>
+  <div class="tt-entity-from-url">{{ drupal_entity('node') }}</div>
+  <div class="tt-field">{{ drupal_field('body', 'node', 1) }}</div>
+  <div class="tt-block">{{ drupal_block('powered_by_drupal') }}</div>
+  <div class="tt-token">{{ drupal_token('site:name') }}</div>
+  <div class="tt-config">{{ drupal_config('user.settings', 'anonymous') }}</div>
+  <div class="tt-token-replace">{{ 'Site name: [site:name]' | token_replace }}</div>
+  <div class="tt-preg-replace">{{ 'foo' | preg_replace('(foo)', '$1-bar') }}</div>
+  <div class="tt-image-style">{{ 'public://images/ocean.jpg' | image_style('thumbnail') }}</div>
+</div>
diff --git a/tests/twig_tweak_test/twig_tweak_test.info.yml b/tests/twig_tweak_test/twig_tweak_test.info.yml
new file mode 100644
index 0000000..5982a93
--- /dev/null
+++ b/tests/twig_tweak_test/twig_tweak_test.info.yml
@@ -0,0 +1,8 @@
+name: Twig tweak test
+type: module
+description: Support module for Tweak twig testing.
+package: Testing
+core: 8.x
+dependencies:
+  - twig_tweak
+  - node
diff --git a/tests/twig_tweak_test/twig_tweak_test.module b/tests/twig_tweak_test/twig_tweak_test.module
new file mode 100644
index 0000000..cabd649
--- /dev/null
+++ b/tests/twig_tweak_test/twig_tweak_test.module
@@ -0,0 +1,20 @@
+<?php
+
+/**
+ * @file
+ * Primary module hooks for Twig Tweak test module.
+ */
+
+/**
+ * Implements hook_page_bottom().
+ */
+function twig_tweak_test_page_bottom(array &$page_bottom) {
+  $page_bottom['twig_tweak_test']['#theme'] = 'twig_tweak_test';
+}
+
+/**
+ * Implements hook_theme().
+ */
+function twig_tweak_test_theme() {
+  return ['twig_tweak_test' => ['variables' => []]];
+}