diff --git a/src/Drush/Commands/PackageScannerDrushCommands.php b/src/Drush/Commands/PackageScannerDrushCommands.php
index c694c8b..20dca32 100644
--- a/src/Drush/Commands/PackageScannerDrushCommands.php
+++ b/src/Drush/Commands/PackageScannerDrushCommands.php
@@ -6,14 +6,15 @@
 
 use Consolidation\AnnotatedCommand\CommandResult;
 use Consolidation\OutputFormatters\StructuredData\RowsOfFields;
-use Drupal\Component\DependencyInjection\ContainerInterface;
-use Drupal\helfi_api_base\Package\VersionChecker;
 use DrupalTools\OutputFormatters\MarkdownTableFormatter;
+use DrupalTools\Package\ComposerOutdatedProcess;
+use DrupalTools\Package\VersionChecker;
 use Drush\Attributes\Argument;
+use Drush\Attributes\Bootstrap;
 use Drush\Attributes\Command;
 use Drush\Attributes\FieldLabels;
+use Drush\Boot\DrupalBootLevels;
 use Drush\Commands\DrushCommands;
-use Drush\Drush;
 use Psr\Container\ContainerInterface as DrushContainer;
 
 /**
@@ -24,7 +25,7 @@ final class PackageScannerDrushCommands extends DrushCommands {
   /**
    * Constructs a new instance.
    *
-   * @param \Drupal\helfi_api_base\Package\VersionChecker $versionChecker
+   * @param \DrupalTools\Package\VersionChecker $versionChecker
    *   The version checker service.
    */
   public function __construct(
@@ -36,10 +37,7 @@ public function __construct(
   /**
    * {@inheritdoc}
    */
-  public static function create(ContainerInterface $container, ?DrushContainer $drush = NULL): self {
-    if (!$drush && Drush::hasContainer()) {
-      $drush = Drush::getContainer();
-    }
+  public static function create(DrushContainer $drush): self {
     /** @var \Drush\Formatters\DrushFormatterManager $formatterManager */
     $formatterManager = $drush->get('formatterManager');
 
@@ -47,9 +45,11 @@ public static function create(ContainerInterface $container, ?DrushContainer $dr
     if (!$formatterManager->hasFormatter('markdown_table')) {
       $formatterManager->addFormatter('markdown_table', new MarkdownTableFormatter());
     }
-    return new self(
-      $container->get('helfi_api_base.package_version_checker'),
-    );
+
+    $process = new ComposerOutdatedProcess();
+    $versionChecker = new VersionChecker($process);
+
+    return new self($versionChecker);
   }
 
   /**
@@ -66,6 +66,7 @@ public static function create(ContainerInterface $container, ?DrushContainer $dr
    *   The result.
    */
   #[Command(name: 'helfi:tools:check-composer-versions')]
+  #[Bootstrap(level: DrupalBootLevels::NONE)]
   #[Argument(name: 'file', description: 'Path to composer.lock file')]
   #[FieldLabels(labels: [
     'name' => 'Name',
@@ -75,11 +76,8 @@ public static function create(ContainerInterface $container, ?DrushContainer $dr
   public function checkVersions(?string $file = NULL, array $options = ['format' => 'table']) : CommandResult {
     $rows = [];
     foreach ($this->versionChecker->getOutdated($file) as $version) {
-      /** @var \Drupal\helfi_api_base\Package\Version $version */
-
-      // Skip dev versions since we can't easily verify the latest
-      // version.
-      if ($version->isLatest || str_starts_with($version->version, 'dev-')) {
+      // Skip dev versions since we can't easily verify the latest version.
+      if (str_starts_with($version->version, 'dev-')) {
         continue;
       }
 
diff --git a/src/Package/ComposerOutdatedProcess.php b/src/Package/ComposerOutdatedProcess.php
new file mode 100644
index 0000000..60de629
--- /dev/null
+++ b/src/Package/ComposerOutdatedProcess.php
@@ -0,0 +1,30 @@
+<?php
+
+declare(strict_types=1);
+
+namespace DrupalTools\Package;
+
+use Symfony\Component\Process\Process;
+
+/**
+ * Process for `composer outdated` command.
+ */
+class ComposerOutdatedProcess {
+
+  /**
+   * Runs `composer outdated`.
+   *
+   * @return array
+   *   Decoded JSON from `composer outdated`.
+   *
+   * @throws \Symfony\Component\Process\Exception\ProcessFailedException
+   */
+  public function run(string $workingDir): array {
+    $process = new Process([
+      'composer', 'outdated', '--direct', '--format=json', '--working-dir=' . $workingDir,
+    ]);
+    $process->mustRun();
+    return json_decode($process->getOutput(), TRUE);
+  }
+
+}
diff --git a/src/Package/Exception/VersionCheckException.php b/src/Package/Exception/VersionCheckException.php
new file mode 100644
index 0000000..39e5f3f
--- /dev/null
+++ b/src/Package/Exception/VersionCheckException.php
@@ -0,0 +1,11 @@
+<?php
+
+declare(strict_types=1);
+
+namespace DrupalTools\Package\Exception;
+
+/**
+ * Indicated failure to check versions.
+ */
+class VersionCheckException extends \RuntimeException {
+}
diff --git a/src/Package/Version.php b/src/Package/Version.php
new file mode 100644
index 0000000..891ecf9
--- /dev/null
+++ b/src/Package/Version.php
@@ -0,0 +1,29 @@
+<?php
+
+declare(strict_types=1);
+
+namespace DrupalTools\Package;
+
+/**
+ * A value object to store package version data.
+ */
+final class Version {
+
+  /**
+   * Constructs a new instance.
+   *
+   * @param string $name
+   *   The package name.
+   * @param string $latestVersion
+   *   The latest version.
+   * @param string $version
+   *   The current version.
+   */
+  public function __construct(
+    public string $name,
+    public string $latestVersion,
+    public string $version,
+  ) {
+  }
+
+}
diff --git a/src/Package/VersionChecker.php b/src/Package/VersionChecker.php
new file mode 100644
index 0000000..6d96895
--- /dev/null
+++ b/src/Package/VersionChecker.php
@@ -0,0 +1,74 @@
+<?php
+
+declare(strict_types=1);
+
+namespace DrupalTools\Package;
+
+use DrupalTools\Package\Exception\VersionCheckException;
+use Symfony\Component\Process\Exception\ProcessFailedException;
+
+/**
+ * Provides a package version checker.
+ */
+class VersionChecker {
+
+  /**
+   * Constructs a new instance.
+   */
+  public function __construct(
+    private readonly ComposerOutdatedProcess $process,
+  ) {
+  }
+
+  /**
+   * Gets outdated package versions.
+   *
+   * @param string $composerLockFile
+   *   Path to composer lock file.
+   *
+   * @return \DrupalTools\Package\Version[]
+   *   Outdated packages.
+   *
+   * @throws \DrupalTools\Package\Exception\VersionCheckException
+   */
+  public function getOutdated(string $composerLockFile) : array {
+    $packages = $this->getPackages($composerLockFile);
+    $versions = [];
+
+    foreach ($packages as $packageName => $package) {
+      $versions[] = new Version($packageName, $package['latest'], $package['version']);
+    }
+
+    return $versions;
+  }
+
+  /**
+   * Get outdated packages.
+   *
+   * @throws \DrupalTools\Package\Exception\VersionCheckException
+   */
+  private function getPackages(string $composerLockFile): array {
+    if (!$composerLockFile = realpath($composerLockFile)) {
+      throw new VersionCheckException('Composer lock file not found');
+    }
+
+    $workingDir = dirname($composerLockFile);
+    try {
+      $packages = $this->process->run($workingDir);
+      $packages = $packages['installed'] ?? [];
+    }
+    catch (ProcessFailedException) {
+      throw new VersionCheckException("Composer process failed");
+    }
+
+    $result = [];
+
+    // Key with package name.
+    foreach ($packages as $package) {
+      $result[$package['name']] = $package;
+    }
+
+    return $result;
+  }
+
+}
diff --git a/tests/fixtures/composer.lock b/tests/fixtures/composer.lock
new file mode 100644
index 0000000..ba9dcba
--- /dev/null
+++ b/tests/fixtures/composer.lock
@@ -0,0 +1,50 @@
+{
+    "_readme": [
+        "This file locks the dependencies of your project to a known state",
+        "Read more about it at https://getcomposer.org/doc/01-basic-usage.md#installing-dependencies",
+        "This file is @generated automatically"
+    ],
+    "packages": [
+        {
+            "name": "drupal/helfi_api_base",
+            "version": "1.0.18",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/City-of-Helsinki/drupal-module-helfi-api-base.git",
+                "reference": "e22755ca1b95a9ee142f2edeadc4a1d99a98cb17"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/City-of-Helsinki/drupal-module-helfi-api-base/zipball/e22755ca1b95a9ee142f2edeadc4a1d99a98cb17",
+                "reference": "e22755ca1b95a9ee142f2edeadc4a1d99a98cb17",
+                "shasum": ""
+            },
+            "require": {
+                "drupal/api_tools": "~1.0.0"
+            },
+            "require-dev": {
+                "dealerdirect/phpcodesniffer-composer-installer": "^0.7.0",
+                "drupal/coder": "^8.3"
+            },
+            "type": "drupal-custom-module",
+            "license": [
+                "GPL-2.0-or-later"
+            ],
+            "description": "Helfi - API Base",
+            "support": {
+                "source": "https://github.com/City-of-Helsinki/drupal-module-helfi-api-base/tree/1.0.18",
+                "issues": "https://github.com/City-of-Helsinki/drupal-module-helfi-api-base/issues"
+            },
+            "time": "2021-04-29T07:34:21+00:00"
+        }
+    ],
+    "packages-dev": [],
+    "aliases": [],
+    "minimum-stability": "stable",
+    "stability-flags": [],
+    "prefer-stable": false,
+    "prefer-lowest": false,
+    "platform": [],
+    "platform-dev": [],
+    "plugin-api-version": "2.6.0"
+}
diff --git a/tests/src/Kernel/CheckPackageVersionsCommandsTest.php b/tests/src/Kernel/CheckPackageVersionsCommandsTest.php
index 4019a17..57861ce 100644
--- a/tests/src/Kernel/CheckPackageVersionsCommandsTest.php
+++ b/tests/src/Kernel/CheckPackageVersionsCommandsTest.php
@@ -5,11 +5,12 @@
 namespace Drupal\Tests\helfi_drupal_tools\Kernel;
 
 use Consolidation\OutputFormatters\StructuredData\RowsOfFields;
-use Drupal\helfi_api_base\Package\ComposerOutdatedProcess;
 use Drupal\KernelTests\KernelTestBase;
 use Drupal\Tests\helfi_api_base\Traits\ApiTestTrait;
 use DrupalTools\Drush\Commands\PackageScannerDrushCommands;
 use DrupalTools\OutputFormatters\MarkdownTableFormatter;
+use DrupalTools\Package\ComposerOutdatedProcess;
+use DrupalTools\Package\VersionChecker;
 use Drush\Commands\DrushCommands;
 use Drush\Formatters\DrushFormatterManager;
 use League\Container\Container;
@@ -49,19 +50,10 @@ private function getDrushContainer() : ContainerInterface {
    */
   public function testMarkdownTableFormatter() : void {
     $container = $this->getDrushContainer();
-    PackageScannerDrushCommands::create($this->container, $container);
+    PackageScannerDrushCommands::create($container);
     $this->assertInstanceOf(MarkdownTableFormatter::class, $container->get('formatterManager')->getFormatter('markdown_table'));
   }
 
-  /**
-   * Tests version check with invalid composer.json file.
-   */
-  public function testInvalidComposerFileException() : void {
-    $sut = PackageScannerDrushCommands::create($this->container, $this->getDrushContainer());
-    $this->expectException(\RuntimeException::class);
-    $sut->checkVersions('nonexistent.lock');
-  }
-
   /**
    * Tests version check.
    */
@@ -79,16 +71,15 @@ public function testVersionCheck() : void {
           ],
         ],
       ]);
-    $this->container->set(ComposerOutdatedProcess::class, $process->reveal());
-
-    $sut = PackageScannerDrushCommands::create($this->container, $this->getDrushContainer());
+    $versionChecker = new VersionChecker($process->reveal());
+    $sut = new PackageScannerDrushCommands($versionChecker);
 
     // Test with up-to-date version and make sure we exit with success.
-    $return = $sut->checkVersions();
+    $return = $sut->checkVersions(__DIR__ . '/../../fixtures/composer.lock');
     $this->assertEquals(DrushCommands::EXIT_SUCCESS, $return->getExitCode());
 
     // Test with old version and make sure we exit with failure.
-    $return = $sut->checkVersions();
+    $return = $sut->checkVersions(__DIR__ . '/../../fixtures/composer.lock');
     $this->assertEquals(DrushCommands::EXIT_FAILURE_WITH_CLARITY, $return->getExitCode());
     $rows = $return->getOutputData();
     $this->assertInstanceOf(RowsOfFields::class, $rows);
diff --git a/tests/src/Unit/Package/VersionCheckerTest.php b/tests/src/Unit/Package/VersionCheckerTest.php
new file mode 100644
index 0000000..87b65fa
--- /dev/null
+++ b/tests/src/Unit/Package/VersionCheckerTest.php
@@ -0,0 +1,83 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\helfi_drupal_tools\Unit\Package;
+
+use DrupalTools\Package\ComposerOutdatedProcess;
+use DrupalTools\Package\Exception\VersionCheckException;
+use DrupalTools\Package\Version;
+use DrupalTools\Package\VersionChecker;
+use Drupal\Tests\UnitTestCase;
+use Prophecy\Argument;
+use Prophecy\PhpUnit\ProphecyTrait;
+use Symfony\Component\Process\Exception\ProcessFailedException;
+
+/**
+ * Tests Version checker.
+ *
+ * @group helfi_api_base
+ */
+class VersionCheckerTest extends UnitTestCase {
+
+  use ProphecyTrait;
+
+  /**
+   * Tests missing composer file.
+   */
+  public function testMissingComposerFile(): void {
+    $process = $this->prophesize(ComposerOutdatedProcess::class);
+    $process->run(Argument::any())->willReturn([]);
+    $sut = new VersionChecker($process->reveal());
+
+    $this->expectException(VersionCheckException::class);
+    $sut->getOutdated('nonexistent.lock');
+  }
+
+  /**
+   * Tests composer command failure.
+   */
+  public function testProcessFailure(): void {
+    $process = $this->prophesize(ComposerOutdatedProcess::class);
+    $process
+      ->run(Argument::any())
+      ->shouldBeCalled()
+      ->willThrow($this->prophesize(ProcessFailedException::class)->reveal());
+
+    $sut = new VersionChecker($process->reveal());
+
+    $this->expectException(VersionCheckException::class);
+    $sut->getOutdated(__DIR__ . '/../../../fixtures/composer.lock');
+  }
+
+  /**
+   * Tests getOutdated().
+   */
+  public function testGetOutdated(): void {
+    $process = $this->prophesize(ComposerOutdatedProcess::class);
+    $process
+      ->run(Argument::any())
+      ->shouldBeCalled()
+      ->willReturn([
+        'installed' => [
+          [
+            'name' => 'drupal/helfi_api_base',
+            'version' => '1.0.18',
+            'latest' => '1.1.0',
+          ],
+        ],
+      ]);
+
+    $sut = new VersionChecker($process->reveal());
+
+    $outdated = $sut->getOutdated(__DIR__ . '/../../../fixtures/composer.lock');
+
+    $this->assertNotEmpty($outdated);
+    $outdated = reset($outdated);
+    $this->assertInstanceOf(Version::class, $outdated);
+    $this->assertEquals('drupal/helfi_api_base', $outdated->name);
+    $this->assertEquals('1.0.18', $outdated->version);
+    $this->assertEquals('1.1.0', $outdated->latestVersion);
+  }
+
+}