diff --git a/core/tests/Drupal/Tests/Core/Scripts/TestSiteApplicationTest.php b/core/tests/Drupal/Tests/Core/Scripts/TestSiteApplicationTest.php
index 1f7977f4a3..8019953a82 100644
--- a/core/tests/Drupal/Tests/Core/Scripts/TestSiteApplicationTest.php
+++ b/core/tests/Drupal/Tests/Core/Scripts/TestSiteApplicationTest.php
@@ -39,53 +39,6 @@ protected function setUp() {
     $this->root = dirname(dirname(substr(__DIR__, 0, -strlen(__NAMESPACE__))));
   }
 
-  /**
-   * @coversNothing
-   */
-  public function testInstallWithNonExistingFile() {
-    $php_binary_finder = new PhpExecutableFinder();
-    $php_binary_path = $php_binary_finder->find();
-
-    $command_line = $php_binary_path . ' core/scripts/test-site.php install --setup-file "this-class-does-not-exist" --db-url "' . getenv('SIMPLETEST_DB') . '"';
-    $process = new Process($command_line, $this->root);
-    $process->run();
-
-    $this->assertContains('The file this-class-does-not-exist does not exist.', $process->getErrorOutput());
-    $this->assertSame(1, $process->getExitCode());
-  }
-
-  /**
-   * @coversNothing
-   */
-  public function testInstallWithFileWithNoClass() {
-    $php_binary_finder = new PhpExecutableFinder();
-    $php_binary_path = $php_binary_finder->find();
-
-    $command_line = $php_binary_path . ' core/scripts/test-site.php install --setup-file core/tests/fixtures/empty_file.php.module --db-url "' . getenv('SIMPLETEST_DB') . '"';
-    $process = new Process($command_line, $this->root);
-    $process->run();
-
-    $this->assertContains('The file core/tests/fixtures/empty_file.php.module does not contain a class', $process->getErrorOutput());
-    $this->assertSame(1, $process->getExitCode());
-  }
-
-  /**
-   * @coversNothing
-   */
-  public function testInstallWithNonSetupClass() {
-    $php_binary_finder = new PhpExecutableFinder();
-    $php_binary_path = $php_binary_finder->find();
-
-    // Use __FILE__ to test absolute paths.
-    $command_line = $php_binary_path . ' core/scripts/test-site.php install --setup-file "' . __FILE__ . '" --db-url "' . getenv('SIMPLETEST_DB') . '"';
-    $process = new Process($command_line, $this->root, ['COLUMNS' => PHP_INT_MAX]);
-    $process->run();
-
-    $this->assertContains('The class Drupal\Tests\Core\Scripts\TestSiteApplicationTest contained in', $process->getErrorOutput());
-    $this->assertContains('needs to implement \Drupal\TestSite\TestSetupInterface', $process->getErrorOutput());
-    $this->assertSame(1, $process->getExitCode());
-  }
-
   /**
    * @coversNothing
    */
diff --git a/core/tests/Drupal/Tests/Core/Scripts/TestSiteInstallCommandTest.php b/core/tests/Drupal/Tests/Core/Scripts/TestSiteInstallCommandTest.php
new file mode 100644
index 0000000000..15a9c3a3fe
--- /dev/null
+++ b/core/tests/Drupal/Tests/Core/Scripts/TestSiteInstallCommandTest.php
@@ -0,0 +1,52 @@
+<?php
+
+namespace Drupal\Tests\Core\Scripts;
+
+use Drupal\Tests\UnitTestCase;
+use Drupal\TestSite\TestSiteApplication;
+use Drupal\TestSite\TestSetupInterface;
+use org\bovigo\vfs\vfsStream;
+use Symfony\Component\Console\Tester\CommandTester;
+
+/**
+ * @coversDefaultClass \Drupal\TestSite\Commands\TestSiteInstallCommand
+ *
+ * @group Setup
+ *
+ * @todo Move this into a separate Scripts namespace after
+ *   https://www.drupal.org/project/drupal/issues/2878269
+ */
+class TestSiteInstallCommandTest extends UnitTestCase {
+
+  public function provideSetupFile() {
+    vfsStream::setup('test', NULL, ['FixtureSetupFileClass.php' => '<?php namespace Drupal\Test; class FixtureSetupFileClass {}']);
+    $class = 'Drupal\Test\FixtureSetupFileClass';
+    $file = vfsStream::url('test/FixtureSetupFileClass.php');
+    $interface = TestSetupInterface::class;
+    return [
+      'non-existing-file' => ['The file this-class-does-not-exist does not exist.', 'this-class-does-not-exist'],
+      'no-class' => ['The file core/tests/fixtures/empty_file.php.module does not contain a class', 'core/tests/fixtures/empty_file.php.module'],
+      'non-setup-class' => ["The class $class contained in $file needs to implement \\$interface", $file],
+    ];
+  }
+
+  /**
+   * @covers ::getSetupClass
+   * @dataProvider provideSetupFile
+   */
+  public function testSetupFile($expected, $setup_file) {
+    $app = new TestSiteApplication();
+
+    $command = $app->find('install');
+    $tester = new CommandTester($command);
+
+    $this->expectException(\InvalidArgumentException::class);
+    $this->expectExceptionMessage($expected);
+
+    $tester->execute([
+      'command' => $command->getName(),
+      '--setup-file' => $setup_file,
+    ]);
+  }
+
+}