diff --git a/geshifield/src/Plugin/Field/FieldType/GeshiFieldItem.php b/geshifield/src/Plugin/Field/FieldType/GeshiFieldItem.php
index f7e3407..18ae529 100644
--- a/geshifield/src/Plugin/Field/FieldType/GeshiFieldItem.php
+++ b/geshifield/src/Plugin/Field/FieldType/GeshiFieldItem.php
@@ -49,10 +49,10 @@ class GeshiFieldItem extends FieldItemBase {
    */
   public static function propertyDefinitions(FieldStorageDefinitionInterface $field_definition) {
     $properties['sourcecode'] = DataDefinition::create('string')
-      ->setLabel(t('Source code'));
+      ->setLabel($this->t('Source code'));
 
     $properties['language'] = DataDefinition::create('string')
-      ->setLabel(t('Syntax highlighting mode'));
+      ->setLabel($this->t('Syntax highlighting mode'));
 
     return $properties;
   }
diff --git a/geshifield/src/Plugin/Field/FieldWidget/GeshiFieldDefaultWidget.php b/geshifield/src/Plugin/Field/FieldWidget/GeshiFieldDefaultWidget.php
index 68d89d1..2fd157e 100644
--- a/geshifield/src/Plugin/Field/FieldWidget/GeshiFieldDefaultWidget.php
+++ b/geshifield/src/Plugin/Field/FieldWidget/GeshiFieldDefaultWidget.php
@@ -27,12 +27,12 @@ class GeshiFieldDefaultWidget extends WidgetBase {
     $enabled_languages = GeshiFilter::getEnabledLanguages();
 
     $element['sourcecode'] = array(
-      '#title' => t('Code'),
+      '#title' => $this->t('Code'),
       '#type' => 'textarea',
       '#default_value' => isset($items[$delta]->sourcecode) ? $items[$delta]->sourcecode : NULL,
     );
     $element['language'] = array(
-      '#title' => t('Language'),
+      '#title' => $this->t('Language'),
       '#type' => 'select',
       '#default_value' => isset($items[$delta]->language) ? $items[$delta]->language : NULL,
       '#options' => $enabled_languages,
diff --git a/geshifield/src/Tests/GeshiFieldTest.php b/geshifield/src/Tests/GeshiFieldTest.php
index 6f0efb8..969ba5e 100644
--- a/geshifield/src/Tests/GeshiFieldTest.php
+++ b/geshifield/src/Tests/GeshiFieldTest.php
@@ -101,8 +101,8 @@ class GeshiFieldTest extends WebTestBase {
     foreach ($filters as $filter) {
       $edit['filters[' . $filter . '][status]'] = TRUE;
     }
-    $this->drupalPostForm('admin/config/content/formats/add', $edit, t('Save configuration'));
-    $this->assertRaw(t('Added text format %format.', array('%format' => $edit['name'])), 'New filter created.');
+    $this->drupalPostForm('admin/config/content/formats/add', $edit, $this->t('Save configuration'));
+    $this->assertRaw($this->t('Added text format %format.', array('%format' => $edit['name'])), 'New filter created.');
     $this->drupalGet('admin/config/content/formats');
   }
 
diff --git a/src/Controller/GeshiFilterConflicts.php b/src/Controller/GeshiFilterConflicts.php
index 49cbca8..35e13af 100644
--- a/src/Controller/GeshiFilterConflicts.php
+++ b/src/Controller/GeshiFilterConflicts.php
@@ -18,7 +18,7 @@ class GeshiFilterConflicts extends ControllerBase {
     if (count($conflicts) == 0) {
       $build = array(
         '#type' => 'markup',
-        '#markup' => t('No conflicts found.'),
+        '#markup' => $this->t('No conflicts found.'),
       );
       return $build;
     }
diff --git a/src/Form/GeshiFilterLanguagesForm.php b/src/Form/GeshiFilterLanguagesForm.php
index 26e7fe9..dea9e2c 100644
--- a/src/Form/GeshiFilterLanguagesForm.php
+++ b/src/Form/GeshiFilterLanguagesForm.php
@@ -102,7 +102,7 @@ class GeshiFilterLanguagesForm extends ConfigFormBase {
           foreach ($tags2 as $tag2) {
             if ($tag1 == $tag2) {
               $name = "language[{$language2}][tags]";
-              $form_state->setErrorByName($name, t('The language tags should differ between languages and from the generic tags.'));
+              $form_state->setErrorByName($name, $this->t('The language tags should differ between languages and from the generic tags.'));
             }
           }
         }
@@ -161,8 +161,8 @@ class GeshiFilterLanguagesForm extends ConfigFormBase {
     $config = $this->config('geshifilter.settings');
     $form = array();
     $header = array(
-      t('Language'),
-      t('GeSHi language code'),
+      $this->t('Language'),
+      $this->t('GeSHi language code'),
     );
     if ($add_tag_option) {
       $header[] = $this->t('Tag/language attribute value');
diff --git a/src/Form/GeshiFilterSettingsForm.php b/src/Form/GeshiFilterSettingsForm.php
index ea2f8a9..ddbf3a9 100644
--- a/src/Form/GeshiFilterSettingsForm.php
+++ b/src/Form/GeshiFilterSettingsForm.php
@@ -51,7 +51,7 @@ class GeshiFilterSettingsForm extends ConfigFormBase {
     // library).
     $form['library'] = array(
       '#type' => 'fieldset',
-      '#title' => defined('GESHI_VERSION') ? t('GeSHi library version @version detected', array('@version' => GESHI_VERSION)) : $this->t('GeSHi library'),
+      '#title' => defined('GESHI_VERSION') ? $this->t('GeSHi library version @version detected', array('@version' => GESHI_VERSION)) : $this->t('GeSHi library'),
       '#description' => $this->t('The GeSHi filter requires the GeSHi library (which needs to be @downloaded and installed seperately).', array(
         '@downloaded' => \Drupal::l($this->t('downloaded'), Url::fromUri('http://qbnz.com/highlighter/')),
       )),
diff --git a/src/GeshiFilterCss.php b/src/GeshiFilterCss.php
index aea559c..dd1152b 100644
--- a/src/GeshiFilterCss.php
+++ b/src/GeshiFilterCss.php
@@ -79,7 +79,7 @@ class GeshiFilterCss {
       }
     }
     else {
-      drupal_set_message(t('Error while generating CSS rules: could not load GeSHi library.'), 'error');
+      drupal_set_message($this->t('Error while generating CSS rules: could not load GeSHi library.'), 'error');
     }
     return $output;
   }
diff --git a/src/Plugin/Filter/GeshiFilterFilter.php b/src/Plugin/Filter/GeshiFilterFilter.php
index 19a12c9..9673392 100644
--- a/src/Plugin/Filter/GeshiFilterFilter.php
+++ b/src/Plugin/Filter/GeshiFilterFilter.php
@@ -208,7 +208,7 @@ class GeshiFilterFilter extends FilterBase {
       $tag_style_examples[] = '<code>' . SafeMarkup::checkPlain('[[foo]]') . '</code>';
     }
     if (!$bracket_open) {
-      drupal_set_message(t('Could not determine a valid tag style for GeSHi filtering.'), 'error');
+      drupal_set_message($this->t('Could not determine a valid tag style for GeSHi filtering.'), 'error');
       $bracket_open = SafeMarkup::checkPlain('<');
       $bracket_close = SafeMarkup::checkPlain('>');
     }
@@ -237,7 +237,7 @@ class GeshiFilterFilter extends FilterBase {
           '@lang' => $languages[$tag_to_lang[$tag]],
         ));
       }
-      $items[] = '<li>' . t('Language specific syntax highlighting tags:') . implode(', ', $tags) . '</li>';
+      $items[] = '<li>' . $this->t('Language specific syntax highlighting tags:') . implode(', ', $tags) . '</li>';
       // PHP specific delimiters.
       if (in_array(GeshiFilter::BRACKETS_PHPBLOCK, $tag_styles)) {
         $items[] = $this->t('PHP source code can also be enclosed in &lt;?php ... ?&gt; or &lt;% ... %&gt;, but additional options like line numbering are not possible here.');
@@ -311,26 +311,26 @@ class GeshiFilterFilter extends FilterBase {
       $output .= render($render);
 
       // Defaults.
-      $output .= '<p>' . t('Defaults:') . '</p>';
+      $output .= '<p>' . $this->t('Defaults:') . '</p>';
       $items = array();
       $default_highlighting = $this->config->get('default_highlighting');
       switch ($default_highlighting) {
         case GeshiFilter::DEFAULT_DONOTHING:
-          $description = t("when no language attribute is specified the code
+          $description = $this->t("when no language attribute is specified the code
             block won't be processed by the GeSHi filter");
           break;
 
         case GeshiFilter::DEFAULT_PLAINTEXT:
-          $description = t('when no language attribute is specified, no syntax
+          $description = $this->t('when no language attribute is specified, no syntax
            highlighting will be done');
           break;
 
         default:
-          $description = t('the default language used for syntax highlighting is
+          $description = $this->t('the default language used for syntax highlighting is
             "%default_lang"', array('%default_lang' => $default_highlighting));
           break;
       }
-      $items[] = t('Default highlighting mode for generic syntax highlighting
+      $items[] = $this->t('Default highlighting mode for generic syntax highlighting
         tags: @description.', array('@description' => $description));
       $default_line_numbering = $this->config->get('default_line_numbering');
       switch ($default_line_numbering) {
@@ -364,13 +364,13 @@ class GeshiFilterFilter extends FilterBase {
       foreach ($language_tags as $tag) {
         $tags[] = '<code>' . $bracket_open . SafeMarkup::checkPlain($tag) . $bracket_close . '</code>';
       }
-      $output = t('You can enable syntax highlighting of source code with the following tags: @tags.', array('@tags' => Markup::create(implode(', ', $tags))));
+      $output = $this->t('You can enable syntax highlighting of source code with the following tags: @tags.', array('@tags' => Markup::create(implode(', ', $tags))));
       // Tag style options.
       if (count($tag_style_examples) > 1) {
-        $output .= ' ' . t('The supported tag styles are: @tag_styles.', array('@tag_styles' => Markup::create(implode(', ', $tag_style_examples))));
+        $output .= ' ' . $this->t('The supported tag styles are: @tag_styles.', array('@tag_styles' => Markup::create(implode(', ', $tag_style_examples))));
       }
       if (in_array(GeshiFilter::BRACKETS_PHPBLOCK, $tag_styles)) {
-        $output .= ' ' . t('PHP source code can also be enclosed in &lt;?php ... ?&gt; or &lt;% ... %&gt;.');
+        $output .= ' ' . $this->t('PHP source code can also be enclosed in &lt;?php ... ?&gt; or &lt;% ... %&gt;.');
       }
     }
     return $output;
@@ -452,7 +452,7 @@ class GeshiFilterFilter extends FilterBase {
   foreach ($tags2 as $tag2) {
   if ($tag1 == $tag2) {
   $name = "language[{$language2}][tags]";
-  $form_state->setErrorByName($name, t('The language tags should differ between
+  $form_state->setErrorByName($name, $this->t('The language tags should differ between
   languages and from the generic tags.'));
   }
   }
@@ -573,7 +573,7 @@ class GeshiFilterFilter extends FilterBase {
       $this->t('GeSHi language code'),
     );
     if ($add_tag_option) {
-      $header[] = t('Tag/language attribute value');
+      $header[] = $this->t('Tag/language attribute value');
     }
     $form['language'] = array(
       '#type' => 'table',
diff --git a/src/Tests/GeshiFilterAdministrationTest.php b/src/Tests/GeshiFilterAdministrationTest.php
index ddfbe1c..439f4ae 100644
--- a/src/Tests/GeshiFilterAdministrationTest.php
+++ b/src/Tests/GeshiFilterAdministrationTest.php
@@ -102,14 +102,14 @@ class GeshiFilterAdministrationTest extends WebTestBase {
       'language[php][tags]' => 'php languagetag',
       'language[python][tags]' => 'languagetag python',
     );
-    $this->drupalPostForm('admin/config/content/formats/geshifilter/languages/all', $form_values, t('Save configuration'));
+    $this->drupalPostForm('admin/config/content/formats/geshifilter/languages/all', $form_values, $this->t('Save configuration'));
     $this->assertText($this->t('The language tags should differ between languages and from the generic tags.'), $this->t('Language tags should differ between languages (with generic tag options)'));
 
     // Second round: with format specific tag options.
     // $this->config->set('use_format_specific_options', TRUE);
     // $this->drupalPostForm
     // ('admin/config/content/formats/manage/geshifilter_text_format', array(),
-    // t('Save configuration'));
+    // $this->t('Save configuration'));
     /*$this->config->set('tags_' . $this->input_format_id,
     'code blockcode generictag');
     // A language tag should differ from the generic tags.
@@ -118,9 +118,9 @@ class GeshiFilterAdministrationTest extends WebTestBase {
     'php generictag');
     $this->drupalPostForm('admin/config/content/formats/' .
     $this->input_format_id
-    . '/configure', $form_values, t('Save configuration'));
-    $this->assertText(t('The language tags should differ between languages
-    and from the generic tags.'), t('Language tags should differ from
+    . '/configure', $form_values, $this->t('Save configuration'));
+    $this->assertText($this->t('The language tags should differ between languages
+    and from the generic tags.'), $this->t('Language tags should differ from
     (with format specific tag options)'));
     // Language tags should differ between languages.
     $form_values = array(
@@ -131,10 +131,10 @@ class GeshiFilterAdministrationTest extends WebTestBase {
     );
     $this->drupalPostForm('admin/config/content/formats/' .
     $this->input_format_id .
-    '/configure', $form_values, t('Save configuration'));
-    $this->assertText(t('The language tags should differ between languages
+    '/configure', $form_values, $this->t('Save configuration'));
+    $this->assertText($this->t('The language tags should differ between languages
     and from the
-    generic tags.'), t('Language tags should differ between languages (with
+    generic tags.'), $this->t('Language tags should differ between languages (with
     format specific tag options)'));*/
   }
 
@@ -154,8 +154,8 @@ class GeshiFilterAdministrationTest extends WebTestBase {
     foreach ($filters as $filter) {
       $edit['filters[' . $filter . '][status]'] = TRUE;
     }
-    $this->drupalPostForm('admin/config/content/formats/add', $edit, t('Save configuration'));
-    $this->assertRaw(t('Added text format %format.', array('%format' => $edit['name'])), 'New filter created.');
+    $this->drupalPostForm('admin/config/content/formats/add', $edit, $this->t('Save configuration'));
+    $this->assertRaw($this->t('Added text format %format.', array('%format' => $edit['name'])), 'New filter created.');
     $this->drupalGet('admin/config/content/formats');
   }
 
@@ -166,7 +166,7 @@ class GeshiFilterAdministrationTest extends WebTestBase {
     $edit = array();
     $edit['language[xml][enabled]'] = TRUE;
     $edit['language[xml][tags]'] = "<xml>";
-    $this->drupalPostForm('admin/config/content/formats/geshifilter/languages/all', $edit, t('Save configuration'));
+    $this->drupalPostForm('admin/config/content/formats/geshifilter/languages/all', $edit, $this->t('Save configuration'));
     $this->drupalGet('admin/config/content/formats/geshifilter/languages/all');
     $this->assertFieldChecked('edit-language-xml-enabled', 'The language is enabled.');
     $this->assertRaw('&lt;xml&gt;', 'The tag is defined.');
diff --git a/src/Tests/GeshiFilterCssTest.php b/src/Tests/GeshiFilterCssTest.php
index dfda983..215de4a 100644
--- a/src/Tests/GeshiFilterCssTest.php
+++ b/src/Tests/GeshiFilterCssTest.php
@@ -87,7 +87,7 @@ class GeshiFilterCssTest extends WebTestBase {
     $form_values = array(
       'css_mode' => 2,
     );
-    $this->drupalPostForm('admin/config/content/formats/geshifilter', $form_values, t('Save configuration'));
+    $this->drupalPostForm('admin/config/content/formats/geshifilter', $form_values, $this->t('Save configuration'));
 
     // Create a node.
     $node = array(
@@ -122,8 +122,8 @@ class GeshiFilterCssTest extends WebTestBase {
     foreach ($filters as $filter) {
       $edit['filters[' . $filter . '][status]'] = TRUE;
     }
-    $this->drupalPostForm('admin/config/content/formats/add', $edit, t('Save configuration'));
-    $this->assertRaw(t('Added text format %format.', array('%format' => $edit['name'])), 'New filter created.');
+    $this->drupalPostForm('admin/config/content/formats/add', $edit, $this->t('Save configuration'));
+    $this->assertRaw($this->t('Added text format %format.', array('%format' => $edit['name'])), 'New filter created.');
     $this->drupalGet('admin/config/content/formats');
   }
 
diff --git a/src/Tests/GeshiFilterTest.php b/src/Tests/GeshiFilterTest.php
index 1a6c0b6..a1125cd 100644
--- a/src/Tests/GeshiFilterTest.php
+++ b/src/Tests/GeshiFilterTest.php
@@ -123,8 +123,8 @@ class GeshiFilterTest extends WebTestBase {
     foreach ($filters as $filter) {
       $edit['filters[' . $filter . '][status]'] = TRUE;
     }
-    $this->drupalPostForm('admin/config/content/formats/add', $edit, t('Save configuration'));
-    $this->assertRaw(t('Added text format %format.', array('%format' => $edit['name'])), 'New filter created.');
+    $this->drupalPostForm('admin/config/content/formats/add', $edit, $this->t('Save configuration'));
+    $this->assertRaw($this->t('Added text format %format.', array('%format' => $edit['name'])), 'New filter created.');
     $this->drupalGet('admin/config/content/formats');
   }
 
@@ -195,38 +195,38 @@ class GeshiFilterTest extends WebTestBase {
     // Check language argument.
     $this->assertGeshiFilterHighlighting('<code type="cpp">' . $source_code . '</code>',
       array(array($source_code, 'cpp', 0, 1, FALSE)),
-      t('Checking type="..." argument'));
+      $this->t('Checking type="..." argument'));
     $this->assertGeshiFilterHighlighting('<code lang="cpp">' . $source_code . '</code>',
       array(array($source_code, 'cpp', 0, 1, FALSE)),
-      t('Checking lang="..." argument'));
+      $this->t('Checking lang="..." argument'));
     $this->assertGeshiFilterHighlighting('<code language="cpp">' . $source_code . '</code>',
       array(array($source_code, 'cpp', 0, 1, FALSE)),
-      t('Checking language="..." argument'));
+      $this->t('Checking language="..." argument'));
 
     // Check some languages.
     $languages = array('c', 'cpp', 'java');
     foreach ($languages as $lang) {
       $this->assertGeshiFilterHighlighting('<code language="' . $lang . '">' .
         $source_code . '</code>', array(array($source_code, $lang, 0, 1, FALSE)),
-        t('Checking language="@lang"', array('@lang' => $lang)));
+        $this->t('Checking language="@lang"', array('@lang' => $lang)));
     }
 
     // Check line_numbering argument.
     $this->assertGeshiFilterHighlighting('<code type="cpp" linenumbers="off">' . $source_code . '</code>',
       array(array($source_code, 'cpp', 0, 1, FALSE)),
-      t('Checking linenumbers="off" argument'));
+      $this->t('Checking linenumbers="off" argument'));
     $this->assertGeshiFilterHighlighting('<code type="cpp" linenumbers="normal">' . $source_code . '</code>',
       array(array($source_code, 'cpp', 1, 1, FALSE)),
-      t('Checking linenumbers="normal" argument'));
+      $this->t('Checking linenumbers="normal" argument'));
     $this->assertGeshiFilterHighlighting('<code type="cpp" start="27">' . $source_code . '</code>',
       array(array($source_code, 'cpp', 1, 27, FALSE)),
-      t('Checking start="27" argument'));
+      $this->t('Checking start="27" argument'));
     $this->assertGeshiFilterHighlighting('<code type="cpp" linenumbers="fancy">' . $source_code . '</code>',
       array(array($source_code, 'cpp', 5, 1, FALSE)),
-      t('Checking linenumbers="fancy" argument'));
+      $this->t('Checking linenumbers="fancy" argument'));
     $this->assertGeshiFilterHighlighting('<code type="cpp" fancy="3">' . $source_code . '</code>',
       array(array($source_code, 'cpp', 3, 1, FALSE)),
-      t('Checking fancy="3" argument'));
+      $this->t('Checking fancy="3" argument'));
   }
 
   /**
@@ -245,17 +245,17 @@ class GeshiFilterTest extends WebTestBase {
     // This should be filtered.
     $this->assertGeshiFilterHighlighting('<code language="cpp">' . $source_code . '</code>',
       array(array($source_code, 'cpp', 0, 1, FALSE)),
-      t('Checking angle brackets style in GeshiFilter::BRACKETS_ANGLE mode'));
+      $this->t('Checking angle brackets style in GeshiFilter::BRACKETS_ANGLE mode'));
     // This should not be filtered.
     $this->assertGeshiFilterHighlighting('[code language="cpp"]' . $source_code . '[/code]',
       array(array($source_code, NULL, 0, 1, FALSE)),
-      t('Checking [foo] brackets style in GeshiFilter::BRACKETS_ANGLE mode'));
+      $this->t('Checking [foo] brackets style in GeshiFilter::BRACKETS_ANGLE mode'));
     $this->assertGeshiFilterHighlighting('[[code language="cpp"]]' . $source_code . '[[/code]]',
       array(array($source_code, NULL, 0, 1, FALSE)),
-      t('Checking [[foo]] brackets style in GeshiFilter::BRACKETS_ANGLE mode'));
+      $this->t('Checking [[foo]] brackets style in GeshiFilter::BRACKETS_ANGLE mode'));
     $this->assertGeshiFilterHighlighting('<?php' . $source_code . '?>',
       array(array($source_code, NULL, 0, 1, FALSE)),
-      t('Checking php code blocks in GeshiFilter::BRACKETS_ANGLE mode'));
+      $this->t('Checking php code blocks in GeshiFilter::BRACKETS_ANGLE mode'));
   }
 
   /**
@@ -273,17 +273,17 @@ class GeshiFilterTest extends WebTestBase {
     // This should be filtered.
     $this->assertGeshiFilterHighlighting('[code language="cpp"]' . $source_code . '[/code]',
       array(array($source_code, 'cpp', 0, 1, FALSE)),
-      t('Checking [foo] brackets style in GeshiFilter::BRACKETS_SQUARE mode'));
+      $this->t('Checking [foo] brackets style in GeshiFilter::BRACKETS_SQUARE mode'));
     // This should not be filtered.
     $this->assertGeshiFilterHighlighting('<code language="cpp">' . $source_code . '</code>',
       array(array($source_code, NULL, 0, 1, FALSE)),
-      t('Checking angle brackets style in GeshiFilter::BRACKETS_SQUARE mode'));
+      $this->t('Checking angle brackets style in GeshiFilter::BRACKETS_SQUARE mode'));
     $this->assertGeshiFilterHighlighting('[[code language="cpp"]]' . $source_code . '[[/code]]',
       array(array($source_code, NULL, 0, 1, FALSE)),
-      t('Checking [[foo]] brackets style in GeshiFilter::BRACKETS_SQUARE mode'));
+      $this->t('Checking [[foo]] brackets style in GeshiFilter::BRACKETS_SQUARE mode'));
     $this->assertGeshiFilterHighlighting('<?php' . $source_code . '?>',
       array(array($source_code, NULL, 0, 1, FALSE)),
-      t('Checking php code blocks in GeshiFilter::BRACKETS_SQUARE mode'));
+      $this->t('Checking php code blocks in GeshiFilter::BRACKETS_SQUARE mode'));
   }
 
   /**
@@ -302,17 +302,17 @@ class GeshiFilterTest extends WebTestBase {
     // This should be filtered.
     $this->assertGeshiFilterHighlighting('[[code language="cpp"]]' . $source_code . '[[/code]]',
       array(array($source_code, 'cpp', 0, 1, FALSE)),
-      t('Checking [[foo]] brackets style in GeshiFilter::BRACKETS_DOUBLESQUARE mode'));
+      $this->t('Checking [[foo]] brackets style in GeshiFilter::BRACKETS_DOUBLESQUARE mode'));
     // This should not be filtered.
     $this->assertGeshiFilterHighlighting('<code language="cpp">' . $source_code . '</code>',
       array(array($source_code, NULL, 0, 1, FALSE)),
-      t('Checking angle brackets style in GeshiFilter::BRACKETS_DOUBLESQUARE mode'));
+      $this->t('Checking angle brackets style in GeshiFilter::BRACKETS_DOUBLESQUARE mode'));
     $this->assertGeshiFilterHighlighting('[code language="cpp"]' . $source_code . '[/code]',
       array(array($source_code, NULL, 0, 1, FALSE)),
-      t('Checking [foo] brackets style in GeshiFilter::BRACKETS_DOUBLESQUARE mode'));
+      $this->t('Checking [foo] brackets style in GeshiFilter::BRACKETS_DOUBLESQUARE mode'));
     $this->assertGeshiFilterHighlighting('<?php' . $source_code . '?>',
       array(array($source_code, NULL, 0, 1, FALSE)),
-      t('Checking php code blocks in GeshiFilter::BRACKETS_DOUBLESQUARE mode'));
+      $this->t('Checking php code blocks in GeshiFilter::BRACKETS_DOUBLESQUARE mode'));
   }
 
   /**
@@ -331,17 +331,17 @@ class GeshiFilterTest extends WebTestBase {
     // This should be filtered.
     $this->assertGeshiFilterHighlighting('<?php' . $source_code . '?>',
       array(array($source_code, 'php', 0, 1, FALSE)),
-      t('Checking php code blocks in GeshiFilter::BRACKETS_PHPBLOCK mode'));
+      $this->t('Checking php code blocks in GeshiFilter::BRACKETS_PHPBLOCK mode'));
     // This should not be filtered.
     $this->assertGeshiFilterHighlighting('<code language="cpp">' . $source_code . '</code>',
       array(array($source_code, NULL, 0, 1, FALSE)),
-      t('Checking angle brackets style in GeshiFilter::BRACKETS_PHPBLOCK mode'));
+      $this->t('Checking angle brackets style in GeshiFilter::BRACKETS_PHPBLOCK mode'));
     $this->assertGeshiFilterHighlighting('[code language="cpp"]' . $source_code . '[/code]',
       array(array($source_code, NULL, 0, 1, FALSE)),
-      t('Checking [foo] brackets style in GeshiFilter::BRACKETS_PHPBLOCK mode'));
+      $this->t('Checking [foo] brackets style in GeshiFilter::BRACKETS_PHPBLOCK mode'));
     $this->assertGeshiFilterHighlighting('[[code language="cpp"]]' . $source_code . '[[/code]]',
       array(array($source_code, NULL, 0, 1, FALSE)),
-      t('Checking [[foo]] brackets style in GeshiFilter::BRACKETS_PHPBLOCK mode'));
+      $this->t('Checking [[foo]] brackets style in GeshiFilter::BRACKETS_PHPBLOCK mode'));
   }
 
   /**
@@ -361,10 +361,10 @@ class GeshiFilterTest extends WebTestBase {
     // Test the tags.
     $this->assertGeshiFilterHighlighting('<c++>' . $source_code . '</c++>',
       array(array($source_code, 'cpp', 0, 1, FALSE)),
-      t('Checking <c++>..</c++>'));
+      $this->t('Checking <c++>..</c++>'));
     $this->assertGeshiFilterHighlighting('<c#>' . $source_code . '</c#>',
       array(array($source_code, 'csharp', 0, 1, FALSE)),
-      t('Checking <c#>..</c#>'));
+      $this->t('Checking <c#>..</c#>'));
   }
 
   /**
@@ -384,10 +384,10 @@ class GeshiFilterTest extends WebTestBase {
     // Test the tags.
     $this->assertGeshiFilterHighlighting('<cpp>' . $source_code . '</cpp>',
       array(array($source_code, 'cpp', 0, 1, FALSE)),
-      t('Source code in <cpp>...</cpp> should work when <c>...</c> is also enabled'));
+      $this->t('Source code in <cpp>...</cpp> should work when <c>...</c> is also enabled'));
     $this->assertGeshiFilterHighlighting('<csharp>' . $source_code . '</csharp>',
       array(array($source_code, 'csharp', 0, 1, FALSE)),
-      t('Source code in <csharp>...</csharp> should work when <c>...</c> is also enabled'));
+      $this->t('Source code in <csharp>...</csharp> should work when <c>...</c> is also enabled'));
   }
 
   /**
@@ -406,15 +406,15 @@ class GeshiFilterTest extends WebTestBase {
     // Tests.
     $this->assertGeshiFilterHighlighting('<code>' . $source_code . '</code>',
       array(array('<code>' . $source_code . '</code>', FALSE, 0, 1, FALSE)),
-      t('Do nothing mode should not touch given source code')
+      $this->t('Do nothing mode should not touch given source code')
     );
     $this->assertGeshiFilterHighlighting('<code language="cpp">' . $source_code . '</code>',
       array(array($source_code, 'cpp', 0, 1, FALSE)),
-      t('Highlighting with language="cpp" should work when default is "do nothing"')
+      $this->t('Highlighting with language="cpp" should work when default is "do nothing"')
     );
     $this->assertGeshiFilterHighlighting('<cpp>' . $source_code . '</cpp>',
       array(array($source_code, 'cpp', 0, 1, FALSE)),
-      t('Highlighting with <cpp>...</cpp> should work when default is "do nothing"')
+      $this->t('Highlighting with <cpp>...</cpp> should work when default is "do nothing"')
     );
   }
 
@@ -426,7 +426,7 @@ class GeshiFilterTest extends WebTestBase {
     // No title set.
     $this->assertGeshiFilterHighlighting('<code language="cpp">' . $source_code . '</code>',
       array(array('geshifilter-title', FALSE, 0, 0, 0)),
-      t('Setting the title attritbute on code block.'),
+      $this->t('Setting the title attritbute on code block.'),
      TRUE
     );
     // Title set.
@@ -439,7 +439,7 @@ class GeshiFilterTest extends WebTestBase {
           0,
         ),
       ),
-      t('Setting the title attritbute on code block.')
+      $this->t('Setting the title attritbute on code block.')
     );
   }
 
@@ -451,7 +451,7 @@ class GeshiFilterTest extends WebTestBase {
     // No title set.
     $this->assertGeshiFilterHighlighting('<code language="cpp">' . $source_code . '</code>',
       array(array('<span class="geshifilter">', FALSE, 0, 0, 0)),
-      t('Setting the title attritbute on inline code.')
+      $this->t('Setting the title attritbute on inline code.')
     );
     // Title set.
     $this->assertGeshiFilterHighlighting('<code language="cpp" title="Foo the bar!">' . $source_code . '</code>',
@@ -464,7 +464,7 @@ class GeshiFilterTest extends WebTestBase {
           0,
         ),
       ),
-      t('Setting the title attritbute on inline code.')
+      $this->t('Setting the title attritbute on inline code.')
     );
   }
 
@@ -483,10 +483,10 @@ class GeshiFilterTest extends WebTestBase {
     // This should be filtered.
     $this->assertGeshiFilterHighlighting('[code]' . $source_code . '[/code]',
       array(array($source_code, 'text', 0, 1, FALSE)),
-      t('Checking if [code][section]...[/code] works'));
+      $this->t('Checking if [code][section]...[/code] works'));
     $this->assertGeshiFilterHighlighting('[code language="ini"]' . $source_code . '[/code]',
       array(array($source_code, 'ini', 0, 1, FALSE)),
-      t('Checking if [code language="ini"][section]...[/code] works'));
+      $this->t('Checking if [code language="ini"][section]...[/code] works'));
   }
 
   /**