diff --git a/tests/Composer/Test/Command/DiagnoseCommandTest.php b/tests/Composer/Test/Command/DiagnoseCommandTest.php
new file mode 100644
index 000000000..e79c9ee49
--- /dev/null
+++ b/tests/Composer/Test/Command/DiagnoseCommandTest.php
@@ -0,0 +1,57 @@
+<?php declare(strict_types=1);
+
+/*
+ * This file is part of Composer.
+ *
+ * (c) Nils Adermann <naderman@naderman.de>
+ *     Jordi Boggiano <j.boggiano@seld.be>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Composer\Test\Command;
+
+use Composer\Test\TestCase;
+
+class DiagnoseCommandTest extends TestCase
+{
+    public function testCmdFail(): void
+    {
+        $this->initTempComposer(['name' => 'foo/bar', 'description' => 'test pkg']);
+
+        $appTester = $this->getApplicationTester();
+        $appTester->run(['command' => 'diagnose']);
+
+        $this->assertSame(1, $appTester->getStatusCode());
+
+        $output = $appTester->getDisplay(true);
+        $this->assertStringContainsString('Checking composer.json: <warning>WARNING</warning>
+<warning>No license specified, it is recommended to do so. For closed-source software you may use "proprietary" as license.</warning>', $output);
+
+        $this->assertStringContainsString('Checking git settings: OK
+Checking http connectivity to packagist: OK
+Checking https connectivity to packagist: OK
+Checking github.com rate limit: OK
+Checking disk free space: ', $output);
+    }
+
+    public function testCmdSuccess(): void
+    {
+        $this->initTempComposer(['name' => 'foo/bar', 'description' => 'test pkg', 'license' => 'MIT']);
+
+        $appTester = $this->getApplicationTester();
+        $appTester->run(['command' => 'diagnose']);
+
+        $appTester->assertCommandIsSuccessful();
+
+        $output = $appTester->getDisplay(true);
+        $this->assertStringContainsString('Checking composer.json: OK', $output);
+
+        $this->assertStringContainsString('Checking git settings: OK
+Checking http connectivity to packagist: OK
+Checking https connectivity to packagist: OK
+Checking github.com rate limit: OK
+Checking disk free space: ', $output);
+    }
+}
diff --git a/tests/Composer/Test/Command/UpdateCommandTest.php b/tests/Composer/Test/Command/UpdateCommandTest.php
index 90b614389..9a12a49bd 100644
--- a/tests/Composer/Test/Command/UpdateCommandTest.php
+++ b/tests/Composer/Test/Command/UpdateCommandTest.php
@@ -28,7 +28,7 @@ class UpdateCommandTest extends TestCase
         $appTester = $this->getApplicationTester();
         $appTester->run(array_merge(['command' => 'update', '--dry-run' => true], $command));
 
-        $this->assertSame(strtr(trim($expected), "\r", ''), strtr(trim($appTester->getDisplay()), "\r", ''));
+        $this->assertSame(trim($expected), trim($appTester->getDisplay(true)));
     }
 
     public function provideUpdates(): \Generator