diff --git a/core/includes/bootstrap.inc b/core/includes/bootstrap.inc
index 86e12c7..094feb6 100644
--- a/core/includes/bootstrap.inc
+++ b/core/includes/bootstrap.inc
@@ -13,6 +13,7 @@
 use Drupal\Core\Session\AccountInterface;
 use Drupal\Core\Site\Settings;
 use Drupal\Core\Utility\Error;
+use Drupal\Core\StringTranslation\TranslatableMarkup;
 
 /**
  * Minimum supported version of PHP.
@@ -292,7 +293,7 @@ function drupal_get_path($type, $name) {
  * @ingroup sanitization
  */
 function t($string, array $args = array(), array $options = array()) {
-  return \Drupal::translation()->translate($string, $args, $options);
+  return new TranslatableMarkup($string, $args, $options);
 }
 
 /**
diff --git a/core/lib/Drupal/Core/StringTranslation/StringTranslationTrait.php b/core/lib/Drupal/Core/StringTranslation/StringTranslationTrait.php
index e67bf2b..fd91ed9 100644
--- a/core/lib/Drupal/Core/StringTranslation/StringTranslationTrait.php
+++ b/core/lib/Drupal/Core/StringTranslation/StringTranslationTrait.php
@@ -71,7 +71,7 @@
    * @ingroup sanitization
    */
   protected function t($string, array $args = array(), array $options = array()) {
-    return $this->getStringTranslation()->translate($string, $args, $options);
+    return new TranslatableMarkup($string, $args, $options, $this->getStringTranslation());
   }
 
   /**
@@ -80,7 +80,7 @@ protected function t($string, array $args = array(), array $options = array()) {
    * @see \Drupal\Core\StringTranslation\TranslationInterface::formatPlural()
    */
   protected function formatPlural($count, $singular, $plural, array $args = array(), array $options = array()) {
-    return $this->getStringTranslation()->formatPlural($count, $singular, $plural, $args, $options);
+    return new PluralTranslatableMarkup($count, $singular, $plural, $args, $options, $this->getStringTranslation());
   }
 
   /**
diff --git a/core/modules/breakpoint/tests/src/Unit/BreakpointTest.php b/core/modules/breakpoint/tests/src/Unit/BreakpointTest.php
index fea2d8f..1ea712c 100644
--- a/core/modules/breakpoint/tests/src/Unit/BreakpointTest.php
+++ b/core/modules/breakpoint/tests/src/Unit/BreakpointTest.php
@@ -9,6 +9,7 @@
 
 use Drupal\breakpoint\Breakpoint;
 use Drupal\Tests\UnitTestCase;
+use Drupal\Core\StringTranslation\TranslatableMarkup;
 
 /**
  * @coversDefaultClass \Drupal\breakpoint\Breakpoint
@@ -65,12 +66,8 @@ protected function setupBreakpoint() {
    */
   public function testGetLabel() {
     $this->pluginDefinition['label'] = 'Test label';
-    $this->stringTranslation->expects($this->once())
-      ->method('translate')
-      ->with($this->pluginDefinition['label'], array(), array('context' => 'breakpoint'))
-      ->will($this->returnValue('Test label translated'));
     $this->setupBreakpoint();
-    $this->assertEquals('Test label translated', $this->breakpoint->getLabel());
+    $this->assertEquals(new TranslatableMarkup('Test label', array(), array('context' => 'breakpoint'), $this->stringTranslation), $this->breakpoint->getLabel());
   }
 
   /**
diff --git a/core/tests/Drupal/Tests/Core/Controller/TitleResolverTest.php b/core/tests/Drupal/Tests/Core/Controller/TitleResolverTest.php
index 1d8c416..e2fca4b 100644
--- a/core/tests/Drupal/Tests/Core/Controller/TitleResolverTest.php
+++ b/core/tests/Drupal/Tests/Core/Controller/TitleResolverTest.php
@@ -12,6 +12,7 @@
 use Symfony\Component\HttpFoundation\ParameterBag;
 use Symfony\Component\HttpFoundation\Request;
 use Symfony\Component\Routing\Route;
+use Drupal\Core\StringTranslation\TranslatableMarkup;
 
 /**
  * @coversDefaultClass \Drupal\Core\Controller\TitleResolver
@@ -55,13 +56,7 @@ protected function setUp() {
   public function testStaticTitle() {
     $request = new Request();
     $route = new Route('/test-route', array('_title' => 'static title'));
-
-    $this->translationManager->expects($this->once())
-      ->method('translate')
-      ->with('static title', array(), array())
-      ->will($this->returnValue('translated title'));
-
-    $this->assertEquals('translated title', $this->titleResolver->getTitle($request, $route));
+    $this->assertEquals(new TranslatableMarkup('static title', array(), array(), $this->translationManager), $this->titleResolver->getTitle($request, $route));
   }
 
   /**
@@ -72,13 +67,7 @@ public function testStaticTitle() {
   public function testStaticTitleWithContext() {
     $request = new Request();
     $route = new Route('/test-route', array('_title' => 'static title', '_title_context' => 'context'));
-
-    $this->translationManager->expects($this->once())
-      ->method('translate')
-      ->with('static title', array(), array('context' => 'context'))
-      ->will($this->returnValue('translated title with context'));
-
-    $this->assertEquals('translated title with context', $this->titleResolver->getTitle($request, $route));
+    $this->assertEquals(new TranslatableMarkup('static title', array(), array('context' => 'context'), $this->translationManager), $this->titleResolver->getTitle($request, $route));
   }
 
   /**
@@ -94,20 +83,14 @@ public function testStaticTitleWithParameter($title, $expected_title) {
     $request->attributes->set('_raw_variables', $raw_variables);
 
     $route = new Route('/test-route', array('_title' => $title));
-
-    $this->translationManager->expects($this->once())
-      ->method('translate')
-      ->with($title, $this->logicalOr($this->arrayHasKey('@test'), $this->arrayHasKey('%test'), $this->arrayHasKey('!test')), array())
-      ->will($this->returnValue('static title value'));
-
     $this->assertEquals($expected_title, $this->titleResolver->getTitle($request, $route));
   }
 
   public function providerTestStaticTitleWithParameter() {
+    $translation_manager = $this->getMock('\Drupal\Core\StringTranslation\TranslationInterface');
     return array(
-      array('static title @test', 'static title value'),
-      array('static title !test', 'static title value'),
-      array('static title %test', 'static title value'),
+      array('static title @test', new TranslatableMarkup('static title @test', ['@test' => 'value', '%test' => 'value', '@test2' => 'value2', '%test2' => 'value2'], array(), $translation_manager)),
+      array('static title %test', new TranslatableMarkup('static title %test', ['@test' => 'value', '%test' => 'value', '@test2' => 'value2', '%test2' => 'value2'], array(), $translation_manager)),
     );
   }
 
diff --git a/core/tests/Drupal/Tests/Core/Datetime/DateTest.php b/core/tests/Drupal/Tests/Core/Datetime/DateTest.php
index 9033e1d..d8abb20 100644
--- a/core/tests/Drupal/Tests/Core/Datetime/DateTest.php
+++ b/core/tests/Drupal/Tests/Core/Datetime/DateTest.php
@@ -12,6 +12,7 @@
 use Drupal\Core\DependencyInjection\ContainerBuilder;
 use Drupal\Tests\UnitTestCase;
 use Symfony\Component\HttpFoundation\Request;
+use Drupal\Core\StringTranslation\TranslatableMarkup;
 
 /**
  * @coversDefaultClass \Drupal\Core\Datetime\DateFormatter
@@ -97,11 +98,10 @@ protected function setUp() {
   public function testFormatInterval($interval, $granularity, $expected, $langcode = NULL) {
     // Mocks a simple formatPlural implementation.
     $this->stringTranslation->expects($this->any())
-      ->method('formatPlural')
-      ->with($this->anything(), $this->anything(), $this->anything(), array(), array('langcode' => $langcode))
-      ->will($this->returnCallback(function($count, $one, $multiple) {
-        return $count == 1 ? $one : str_replace('@count', $count, $multiple);
-      }));
+      ->method('translateString')
+      ->willReturnCallback(function (TranslatableMarkup $arg) {
+        return $arg->getUntranslatedString();
+      });
 
     // Check if the granularity is specified.
     if ($granularity) {
@@ -111,7 +111,7 @@ public function testFormatInterval($interval, $granularity, $expected, $langcode
       $result = $this->dateFormatter->formatInterval($interval);
     }
 
-    $this->assertEquals($expected, $result);
+    $this->assertEquals(new TranslatableMarkup($expected, [], ['langcode' => $langcode], $this->stringTranslation), $result);
   }
 
   /**
@@ -153,14 +153,8 @@ public function providerTestFormatInterval() {
    * Tests the formatInterval method for 0 second.
    */
   public function testFormatIntervalZeroSecond() {
-    $this->stringTranslation->expects($this->once())
-      ->method('translate')
-      ->with('0 sec', array(), array('langcode' => 'xxx-lolspeak'))
-      ->will($this->returnValue('0 sec'));
-
     $result = $this->dateFormatter->formatInterval(0, 1, 'xxx-lolspeak');
-
-    $this->assertEquals('0 sec', $result);
+    $this->assertEquals(new TranslatableMarkup('0 sec', array(), array('langcode' => 'xxx-lolspeak'), $this->stringTranslation), $result);
   }
 
   /**
@@ -267,21 +261,18 @@ public function testformatDiff($expected, $max_age, $timestamp1, $timestamp2, $o
 
     // Mocks a simple formatPlural implementation.
     $this->stringTranslation->expects($this->any())
-      ->method('formatPlural')
-      ->with($this->anything(), $this->anything(), $this->anything(), array(), array('langcode' => isset($options['langcode']) ? $options['langcode'] : NULL))
-      ->will($this->returnCallback(function($count, $one, $multiple) {
-        return $count == 1 ? $one : str_replace('@count', $count, $multiple);
-      }));
-
-    // Mocks a simple translate implementation.
-    $this->stringTranslation->expects($this->any())
-      ->method('translate')
-      ->with($this->anything())
-      ->will($this->returnCallback(function($string, $args, $options) {
-        return $string;
-      }));
+      ->method('translateString')
+      ->willReturnCallback(function (TranslatableMarkup $arg) {
+        return $arg->getUntranslatedString();
+      });
 
-    $this->assertEquals($expected, $this->dateFormatter->formatDiff($timestamp1, $timestamp2, $options));
+    if (isset($options['langcode'])) {
+      $expected_markup = new TranslatableMarkup($expected, [], ['langcode' => $options['langcode']], $this->stringTranslation);
+    }
+    else {
+      $expected_markup = new TranslatableMarkup($expected, [], [], $this->stringTranslation);
+    }
+    $this->assertEquals($expected_markup, $this->dateFormatter->formatDiff($timestamp1, $timestamp2, $options));
 
     $options['return_as_object'] = TRUE;
     $expected_object = new FormattedDateDiff($expected, $max_age);
diff --git a/core/tests/Drupal/Tests/Core/Entity/EntityTypeTest.php b/core/tests/Drupal/Tests/Core/Entity/EntityTypeTest.php
index 6fa1f9c..c970bcf 100644
--- a/core/tests/Drupal/Tests/Core/Entity/EntityTypeTest.php
+++ b/core/tests/Drupal/Tests/Core/Entity/EntityTypeTest.php
@@ -311,15 +311,7 @@ public function testGetGroupLabel() {
     $this->assertSame($default_label, $entity_type->getGroupLabel());
 
     $default_label = new TranslatableMarkup('Other', array(), array('context' => 'Entity type group'));
-    $entity_type = $this->setUpEntityType([]);
-
-    $string_translation = $this->getMock(TranslationInterface::class);
-    $string_translation->expects($this->atLeastOnce())
-      ->method('translate')
-      ->with('Other', array(), array('context' => 'Entity type group'))
-      ->willReturn($default_label);
-    $entity_type->setStringTranslation($string_translation);
-
+    $entity_type = $this->setUpEntityType(array('group_label' => $default_label));
     $this->assertSame($default_label, $entity_type->getGroupLabel());
   }
 
diff --git a/core/tests/Drupal/Tests/Core/StringTranslation/StringTranslationTraitTest.php b/core/tests/Drupal/Tests/Core/StringTranslation/StringTranslationTraitTest.php
index c8000bf..7985c8d 100644
--- a/core/tests/Drupal/Tests/Core/StringTranslation/StringTranslationTraitTest.php
+++ b/core/tests/Drupal/Tests/Core/StringTranslation/StringTranslationTraitTest.php
@@ -7,7 +7,11 @@
 
 namespace Drupal\Tests\Core\StringTranslation;
 
+use Drupal\Core\StringTranslation\PluralTranslatableMarkup;
+use Drupal\Core\StringTranslation\TranslatableMarkup;
+use Drupal\Core\StringTranslation\TranslationInterface;
 use Drupal\Tests\UnitTestCase;
+use Prophecy\Argument;
 
 /**
  * @coversDefaultClass \Drupal\Core\StringTranslation\StringTranslationTrait
@@ -35,11 +39,13 @@ class StringTranslationTraitTest extends UnitTestCase {
    */
   protected function setUp() {
     $this->translation = $this->getObjectForTrait('\Drupal\Core\StringTranslation\StringTranslationTrait');
-    $stub = $this->getStringTranslationStub();
-    $stub->expects($this->any())
-      ->method('formatPlural')
-      ->will($this->returnArgument(2));
-    $this->translation->setStringTranslation($stub);
+    $mock = $this->prophesize(TranslationInterface::class);
+    $mock->translate(Argument::cetera())->shouldNotBeCalled();
+    $mock->formatPlural(Argument::cetera())->shouldNotBeCalled();
+    $mock->translateString(Argument::cetera())->will(function ($args) {
+      return $args[0]->getUntranslatedString();
+    });
+    $this->translation->setStringTranslation($mock->reveal());
     $this->reflection = new \ReflectionClass(get_class($this->translation));
   }
 
@@ -50,7 +56,9 @@ public function testT() {
     $method = $this->reflection->getMethod('t');
     $method->setAccessible(TRUE);
 
-    $this->assertEquals('something', $method->invoke($this->translation, 'something'));
+    $result = $method->invoke($this->translation, 'something');
+    $this->assertInstanceOf(TranslatableMarkup::class, $result);
+    $this->assertEquals('something', $result);
   }
 
   /**
@@ -60,7 +68,9 @@ public function testFormatPlural() {
     $method = $this->reflection->getMethod('formatPlural');
     $method->setAccessible(TRUE);
 
-    $this->assertEquals('apples', $method->invoke($this->translation, 2, 'apple', 'apples'));
+    $result = $method->invoke($this->translation, 2, 'apple', 'apples');
+    $this->assertInstanceOf(PluralTranslatableMarkup::class, $result);
+    $this->assertEquals('apples', $result);
   }
 
 }