Add test and make sure gitattributes are set.

.gitattributes

@@ -0,0 +1,7 @@
+# Define the line ending behavior of the different file extensions
+# Set default behaviour, in case users don't have core.autocrlf set.
+* text=auto
+* text eol=lf
+
+# Declare files that will always have CRLF line endings on checkout.
+*.bat eol=crlf

src/Shell/Task/I18nTask.php

@@ -12,9 +12,9 @@
  * @since         3.0.0
  * @license       http://www.opensource.org/licenses/mit-license.php MIT License
  */
-namespace Cake\Upgrade\Console\Command\Task;
+namespace Cake\Upgrade\Shell\Task;
 
-use Cake\Upgrade\Console\Command\Task\BaseTask;
+use Cake\Upgrade\Shell\Task\BaseTask;
 
 /**
  * I18n Task.

src/Shell/Task/StageTask.php

@@ -266,7 +266,7 @@ public function change($filePath, $original, $updated) {
 	}
 
 /**
- * Get the source of a file, taking account that there may be incremental diffs
+ * Get the source of a file, taking into account that there may be incremental diffs
  *
  * @param string $path
  * @return string

tests/TestCase/Shell/Task/I18nTaskTest.php

@@ -0,0 +1,50 @@
+<?php
+namespace Cake\Upgrade\Test\TestCase\Shell\Task;
+
+use Cake\TestSuite\TestCase;
+use Cake\Upgrade\Shell\Task\I18nTask;
+
+/**
+ * UpgradeShellTest
+ *
+ */
+class I18nTaskTest extends TestCase {
+
+/**
+ * Upgrade shell instance
+ *
+ * @var mixed
+ */
+	public $sut;
+
+/**
+ * setUp
+ *
+ * Create a mock for all tests to use
+ *
+ * @return void
+ */
+	public function setUp() {
+		parent::setUp();
+
+		$io = $this->getMock('Cake\Console\ConsoleIo', [], [], '', false);
+
+		$this->sut = $this->getMock(
+			'Cake\Upgrade\Shell\Task\I18nTask',
+			['in', 'out', 'hr', 'err', '_stop'],
+			[$io]
+		);
+		$this->sut->loadTasks();
+	}
+
+	public function testProcess() {
+		$path = TESTS . 'test_files' . DS;
+		$result = $this->sut->process($path . 'i18n_before.php');
+		$this->assertTrue($result);
+
+		$result = $this->sut->Stage->source($path . 'i18n_before.php');
+		$expected = file_get_contents($path . 'i18n_after.php');
+		$this->assertTextEquals($expected, $result);
+	}
+
+}

tests/test_files/i18n_after.php

@@ -0,0 +1,10 @@
+<?php
+
+class Foo {
+
+	public function test() {
+		$x = __("Some {0} text", $y);
+		$x = __d('Domain', "Some {0} {1} text {2}", $a, $b, $c);
+	}
+
+}

tests/test_files/i18n_before.php

@@ -0,0 +1,10 @@
+<?php
+
+class Foo {
+
+	public function test() {
+		$x = __("Some %s text", $y);
+		$x = __d('Domain', "Some %s %s text %s", $a, $b, $c);
+	}
+
+}