diff --git a/main/src/Console/Command/ClearCommand.php b/main/src/Console/Command/ClearCommand.php
new file mode 100644
index 0000000..de20f4e
--- /dev/null
+++ b/main/src/Console/Command/ClearCommand.php
@@ -0,0 +1,91 @@
+<?php
+
+namespace IntegerNet\Solr\Console\Command;
+
+use IntegerNet\Solr\Indexer\Slice;
+use IntegerNet\Solr\Model\Indexer;
+use Magento\Framework\App;
+use Symfony\Component\Console\Command\Command;
+use Symfony\Component\Console\Helper\ProgressBar;
+use Symfony\Component\Console\Input\InputInterface;
+use Symfony\Component\Console\Input\InputOption;
+use Symfony\Component\Console\Output\OutputInterface;
+use Symfony\Component\Console\Style\SymfonyStyle;
+
+/**
+ * solr:clear command
+ */
+class ClearCommand extends Command
+{
+    const INPUT_STORES      = 'stores';
+    const INPUT_USESWAPCORE = 'useswapcore';
+    /**
+     * @var Indexer\Console
+     */
+    private $indexer;
+    /**
+     * @var App\State
+     */
+    private $appState;
+
+    public function __construct(Indexer\Console $indexer, App\State $appState, $name = null)
+    {
+        parent::__construct($name);
+        $this->indexer = $indexer;
+        $this->appState = $appState;
+    }
+
+    protected function configure()
+    {
+        $options = [
+            new InputOption(
+                self::INPUT_STORES,
+                null,
+                InputOption::VALUE_OPTIONAL,
+                'Clear solr product index for given stores (can be store id, store code, comma seperated. Or "all".) '
+                . 'If not set, clear all stores.'
+            ),
+            new InputOption(
+                self::INPUT_USESWAPCORE,
+                null,
+                InputOption::VALUE_NONE,
+                'Use swap core for clearing instead of live solr core (only if configured correctly).'
+            ),
+            ];
+        $this->setName('solr:clear');
+        $this->setHelp('Clear Solr index for given stores (see "stores" param).');
+        $this->setDescription('Clear Solr index');
+        $this->setDefinition($options);
+    }
+
+    protected function execute(InputInterface $input, OutputInterface $output)
+    {
+        $styledOutput = new StyledOutput(
+            $output,
+            class_exists(SymfonyStyle::class) ? new SymfonyStyle($input, $output) : null
+        );
+        $startTime = microtime(true);
+        $this->appState->setAreaCode(App\Area::AREA_GLOBAL);
+        if (!$input->getOption(self::INPUT_STORES) || $input->getOption(self::INPUT_STORES) === 'all') {
+            $stores = null;
+            $styledOutput->title('Clearing full Solr product index...');
+        } else {
+            $stores = \explode(',', $input->getOption(self::INPUT_STORES));
+            $styledOutput->title('Clearing Solr product index for stores ' . \implode(', ', $stores) . '...');
+        }
+        try {
+            $this->indexer->addProgressHandler(
+                new ProgressInConsole($output)
+            );
+            if ($input->getOption(self::INPUT_USESWAPCORE)) {
+                $this->indexer->clearStoresOnSwappedCore($stores);
+            } else {
+                $this->indexer->clearStores($stores);
+            }
+            $totalTime = number_format(microtime(true) - $startTime, 2);
+            $styledOutput->success("Clearing finished in $totalTime seconds.");
+        } catch (\Exception $e) {
+            $styledOutput->error($e->getMessage());
+        }
+    }
+}
\ No newline at end of file
diff --git a/main/src/Console/Command/ReindexCommand.php b/main/src/Console/Command/ReindexCommand.php
index a7a5813..b3de0be 100644
--- a/main/src/Console/Command/ReindexCommand.php
+++ b/main/src/Console/Command/ReindexCommand.php
@@ -17,7 +17,10 @@
  */
 class ReindexCommand extends Command
 {
-    const INPUT_STORES = 'stores';
+    const INPUT_STORES       = 'stores';
+    const INPUT_EMPTYINDEX   = 'emptyindex';
+    const INPUT_NOEMPTYINDEX = 'noemptyindex';
+    const INPUT_PROGRESS     = 'progress';
     /**
      * @var Indexer\Console
      */
@@ -38,26 +41,26 @@ protected function configure()
     {
         $options = [
             new InputOption(
-                'stores',
+                self::INPUT_STORES,
                 null,
                 InputOption::VALUE_OPTIONAL,
                 'Reindex given stores (can be store id, store code, comma seperated. Or "all".) '
                 . 'If not set, reindex all stores.'
             ),
             new InputOption(
-                'emptyindex',
+                self::INPUT_EMPTYINDEX,
                 null,
                 InputOption::VALUE_NONE,
                 'Force emptying the solr index for the given store(s). If not set, configured value is used.'
             ),
             new InputOption(
-                'noemptyindex',
+                self::INPUT_NOEMPTYINDEX,
                 null,
                 InputOption::VALUE_NONE,
                 'Force not emptying the solr index for the given store(s). If not set, configured value is used.'
             ),
             new InputOption(
-                'progress',
+                self::INPUT_PROGRESS,
                 null,
                 InputOption::VALUE_NONE,
                 'Show progress bar.'
@@ -88,13 +91,13 @@ class_exists(SymfonyStyle::class) ? new SymfonyStyle($input, $output) : null
             $this->indexer->addProgressHandler(
                 new ProgressInConsole(
                     $output,
-                    $input->getOption('progress') ? ProgressInConsole::USE_PROGRESS_BAR : false
+                    $input->getOption(self::INPUT_PROGRESS) ? ProgressInConsole::USE_PROGRESS_BAR : false
                 )
             );
-            if ($input->getOption('emptyindex')) {
+            if ($input->getOption(self::INPUT_EMPTYINDEX)) {
                 $styledOutput->note('Forcing empty index.');
                 $this->indexer->executeStoresForceEmpty($stores);
-            } elseif ($input->getOption('noemptyindex')) {
+            } elseif ($input->getOption(self::INPUT_NOEMPTYINDEX)) {
                 $styledOutput->note('Forcing non-empty index.');
                 $this->indexer->executeStoresForceNotEmpty($stores);
             } else {
diff --git a/main/src/Console/Command/ReindexSliceCommand.php b/main/src/Console/Command/ReindexSliceCommand.php
index c954aee..33cc799 100644
--- a/main/src/Console/Command/ReindexSliceCommand.php
+++ b/main/src/Console/Command/ReindexSliceCommand.php
@@ -17,7 +17,10 @@
  */
 class ReindexSliceCommand extends Command
 {
-    const INPUT_STORES = 'stores';
+    const INPUT_STORES      = 'stores';
+    const INPUT_SLICE       = 'slice';
+    const INPUT_USESWAPCORE = 'useswapcore';
+    const INPUT_PROGRESS    = 'progress';
     /**
      * @var Indexer\Console
      */
@@ -38,33 +41,36 @@ protected function configure()
     {
         $options = [
             new InputOption(
-                'stores',
+                self::INPUT_STORES,
                 null,
                 InputOption::VALUE_OPTIONAL,
                 'Reindex given stores (can be store id, store code, comma seperated. Or "all".) '
                 . 'If not set, reindex all stores.'
             ),
             new InputOption(
-                'slice',
+                self::INPUT_SLICE,
                 null,
                 InputOption::VALUE_REQUIRED,
                 '<number>/<total_number>, i.e. "1/5" or "2/5". '
             ),
             new InputOption(
-                'useswapcore',
+                self::INPUT_USESWAPCORE,
                 null,
                 InputOption::VALUE_NONE,
                 'Use swap core for indexing instead of live solr core (only if configured correctly).'
             ),
             new InputOption(
-                'progress',
+                self::INPUT_PROGRESS,
                 null,
                 InputOption::VALUE_NONE,
                 'Show progress bar.'
             )
         ];
         $this->setName('solr:reindex:slice');
-        $this->setHelp('Partially reindex Solr for given stores (see "stores" param). Can be used for letting indexing run in parallel.');
+        $this->setHelp(
+            'Partially reindex Solr for given stores (see "stores" param). '
+            . 'Can be used for letting indexing run in parallel.'
+        );
         $this->setDescription('Partially reindex Solr');
         $this->setDefinition($options);
     }
@@ -88,17 +94,20 @@ class_exists(SymfonyStyle::class) ? new SymfonyStyle($input, $output) : null
             $this->indexer->addProgressHandler(
                 new ProgressInConsole(
                     $output,
-                    $input->getOption('progress') ? ProgressInConsole::USE_PROGRESS_BAR : false
+                    $input->getOption(self::INPUT_PROGRESS) ? ProgressInConsole::USE_PROGRESS_BAR : false
                 )
             );
-            $styledOutput->note('Processing slice ' . $input->getOption('slice') . '...');
-            if ($input->getOption('useswapcore')) {
+            $styledOutput->note('Processing slice ' . $input->getOption(self::INPUT_SLICE) . '...');
+            if ($input->getOption(self::INPUT_USESWAPCORE)) {
                 $this->indexer->executeStoresSliceOnSwappedCore(
-                    Slice::fromExpression($input->getOption('slice')),
+                    Slice::fromExpression($input->getOption(self::INPUT_SLICE)),
                     $stores
                 );
             } else {
-                $this->indexer->executeStoresSlice(Slice::fromExpression($input->getOption('slice')), $stores);
+                $this->indexer->executeStoresSlice(
+                    Slice::fromExpression($input->getOption(self::INPUT_SLICE)),
+                    $stores
+                );
             }
             $totalTime = number_format(microtime(true) - $startTime, 2);
             $styledOutput->success("Reindex finished in $totalTime seconds.");
diff --git a/main/src/Console/Command/SwapCommand.php b/main/src/Console/Command/SwapCommand.php
new file mode 100644
index 0000000..c7ce148
--- /dev/null
+++ b/main/src/Console/Command/SwapCommand.php
@@ -0,0 +1,84 @@
+<?php
+
+namespace IntegerNet\Solr\Console\Command;
+
+use IntegerNet\Solr\Indexer\Slice;
+use IntegerNet\Solr\Model\Indexer;
+use Magento\Framework\App;
+use Symfony\Component\Console\Command\Command;
+use Symfony\Component\Console\Helper\ProgressBar;
+use Symfony\Component\Console\Input\InputInterface;
+use Symfony\Component\Console\Input\InputOption;
+use Symfony\Component\Console\Output\OutputInterface;
+use Symfony\Component\Console\Style\SymfonyStyle;
+
+/**
+ * solr:swap command
+ */
+class SwapCommand extends Command
+{
+    const INPUT_STORES      = 'stores';
+
+    /**
+     * @var Indexer\Console
+     */
+    private $indexer;
+    /**
+     * @var App\State
+     */
+    private $appState;
+
+    public function __construct(Indexer\Console $indexer, App\State $appState, $name = null)
+    {
+        parent::__construct($name);
+        $this->indexer = $indexer;
+        $this->appState = $appState;
+    }
+
+    protected function configure()
+    {
+        $options = [
+            new InputOption(
+                self::INPUT_STORES,
+                null,
+                InputOption::VALUE_OPTIONAL,
+                'Swap cores for given stores (can be store id, store code, comma seperated. Or "all".) '
+                . 'If not set, swap cores for all stores.'
+            ),
+        ];
+        $this->setName('solr:swap');
+        $this->setHelp(
+            'Swap cores. This is useful if using slices (see solr:reindex:slice) '
+            . 'after indexing with the "--use_swap_core" param; it\'s not needed otherwise.'
+        );
+        $this->setDescription('Swap cores');
+        $this->setDefinition($options);
+    }
+
+    protected function execute(InputInterface $input, OutputInterface $output)
+    {
+        $styledOutput = new StyledOutput(
+            $output,
+            class_exists(SymfonyStyle::class) ? new SymfonyStyle($input, $output) : null
+        );
+        $startTime = microtime(true);
+        $this->appState->setAreaCode(App\Area::AREA_GLOBAL);
+        if (!$input->getOption(self::INPUT_STORES) || $input->getOption(self::INPUT_STORES) === 'all') {
+            $stores = null;
+            $styledOutput->title('Swap all cores...');
+        } else {
+            $stores = \explode(',', $input->getOption(self::INPUT_STORES));
+            $styledOutput->title('Swap cores for stores ' . \implode(', ', $stores) . '...');
+        }
+        try {
+            $this->indexer->addProgressHandler(
+                new ProgressInConsole($output)
+            );
+            $this->indexer->swapCores($stores);
+            $totalTime = number_format(microtime(true) - $startTime, 2);
+            $styledOutput->success("Core swap finished in $totalTime seconds.");
+        } catch (\Exception $e) {
+            $styledOutput->error($e->getMessage());
+        }
+    }
+}
\ No newline at end of file
diff --git a/main/src/Model/Indexer/Console.php b/main/src/Model/Indexer/Console.php
index 416b4bf..abc1c3c 100644
--- a/main/src/Model/Indexer/Console.php
+++ b/main/src/Model/Indexer/Console.php
@@ -13,6 +13,7 @@
 use IntegerNet\Solr\Indexer\ProductIndexer;
 use IntegerNet\Solr\Indexer\Progress\ProgressHandler;
 use IntegerNet\Solr\Indexer\Slice;
+use Magento\Store\Api\Data\StoreInterface;
 use Magento\Store\Model\StoreManagerInterface;
 
 class Console
@@ -64,15 +65,42 @@ public function executeStoresSliceOnSwappedCore($slice, $storeIds)
 
     public function clearStores(array $storeIds = null)
     {
-        //TODO fetch all store ids if NULL
         if (empty($storeIds)) {
-            throw new \BadMethodCallException("Command for 'clear all stores' not implemented yet");
+            $storeIds = array_map(
+                function (StoreInterface $store) {
+                    return $store->getId();
+                },
+                $this->storeManager->getStores()
+            );
         }
         foreach ($this->getStoreIds($storeIds) as $storeId) {
             $this->solrIndexer->clearIndex($storeId);
         }
     }
 
+    public function clearStoresOnSwappedCore(array $storeIds = null)
+    {
+        if (empty($storeIds)) {
+            $storeIds = array_map(
+                function (StoreInterface $store) {
+                    return $store->getId();
+                },
+                $this->storeManager->getStores()
+            );
+        }
+        $this->solrIndexer->activateSwapCore();
+        foreach ($this->getStoreIds($storeIds) as $storeId) {
+            $this->solrIndexer->clearIndex($storeId);
+        }
+        $this->solrIndexer->deactivateSwapCore();
+    }
+
+    public function swapCores(array $storeIds = null)
+    {
+        $this->solrIndexer->checkSwapCoresConfiguration($storeIds);
+        $this->solrIndexer->swapCores($storeIds);
+    }
+
     public function addProgressHandler(ProgressHandler $handler)
     {
         $this->solrIndexer->addProgressHandler($handler);
@@ -122,7 +150,7 @@ function ($storeId) use ($storesByCode) {
                 if (isset($storesByCode[$storeId])) {
                     return $storesByCode[$storeId]->getId();
                 }
-                throw new \InvalidArgumentException("'$storeId' is neither a numric ID nor an existing store code");
+                throw new \InvalidArgumentException("'$storeId' is neither a numeric ID nor an existing store code");
             },
             $storeIds
         );
diff --git a/main/src/etc/di.xml b/main/src/etc/di.xml
index cd2d98a..a4a9f2d 100755
--- a/main/src/etc/di.xml
+++ b/main/src/etc/di.xml
@@ -155,6 +155,8 @@
       <argument name="commands" xsi:type="array">
         <item name="solr_reindex_full" xsi:type="object">IntegerNet\Solr\Console\Command\ReindexCommand</item>
         <item name="solr_reindex_slice" xsi:type="object">IntegerNet\Solr\Console\Command\ReindexSliceCommand</item>
+        <item name="solr_clear" xsi:type="object">IntegerNet\Solr\Console\Command\ClearCommand</item>
+        <item name="solr_swap" xsi:type="object">IntegerNet\Solr\Console\Command\SwapCommand</item>
       </argument>
     </arguments>
   </type>
@@ -170,6 +172,17 @@
       <argument name="appState" xsi:type="object">\Magento\Framework\App\State\Proxy</argument>
     </arguments>
   </type>
+  <type name="IntegerNet\Solr\Console\Command\ClearCommand">
+    <arguments>
+      <argument name="indexer" xsi:type="object">\IntegerNet\Solr\Model\Indexer\Console\Proxy</argument>
+      <argument name="appState" xsi:type="object">\Magento\Framework\App\State\Proxy</argument>
+    </arguments>
+  </type>  <type name="IntegerNet\Solr\Console\Command\SwapCommand">
+    <arguments>
+      <argument name="indexer" xsi:type="object">\IntegerNet\Solr\Model\Indexer\Console\Proxy</argument>
+      <argument name="appState" xsi:type="object">\Magento\Framework\App\State\Proxy</argument>
+    </arguments>
+  </type>
 
 
 
diff --git a/main/test/integration/Console/CommandListTest.php b/main/test/integration/Console/CommandListTest.php
index 1373a07..afffc64 100644
--- a/main/test/integration/Console/CommandListTest.php
+++ b/main/test/integration/Console/CommandListTest.php
@@ -28,7 +28,7 @@ public function testContainsReindexProductsCommand()
         );
         $reindexCommand = $commands['solr_reindex_full'];
         $this->assertEquals('solr:reindex:full', $reindexCommand->getName(), 'Command name');
-        $this->assertInstanceof(
+        $this->assertInstanceOf(
             Command\ReindexCommand::class,
             $reindexCommand,
             'Command should be instantiated.'
@@ -45,13 +45,47 @@ public function testContainsReindexSliceCommand()
         );
         $reindexCommand = $commands['solr_reindex_slice'];
         $this->assertEquals('solr:reindex:slice', $reindexCommand->getName(), 'Command name');
-        $this->assertInstanceof(
+        $this->assertInstanceOf(
             Command\ReindexSliceCommand::class,
             $reindexCommand,
             'Command should be instantiated.'
         );
     }
 
+    public function testContainsClearCommand()
+    {
+        $commands = $this->commandList->getCommands();
+        $this->assertArrayHasKey(
+            'solr_clear',
+            $commands,
+            'Command should be listed'
+        );
+        $clearCommand = $commands['solr_clear'];
+        $this->assertEquals('solr:clear', $clearCommand->getName(), 'Command name');
+        $this->assertInstanceOf(
+            Command\ClearCommand::class,
+            $clearCommand,
+            'Command should be instantiated.'
+        );
+    }
+
+    public function testContainsSwapCommand()
+    {
+        $commands = $this->commandList->getCommands();
+        $this->assertArrayHasKey(
+            'solr_swap',
+            $commands,
+            'Command should be listed'
+        );
+        $clearCommand = $commands['solr_swap'];
+        $this->assertEquals('solr:swap', $clearCommand->getName(), 'Command name');
+        $this->assertInstanceOf(
+            Command\SwapCommand::class,
+            $clearCommand,
+            'Command should be instantiated.'
+        );
+    }
+
     protected function setUp()
     {
         $this->fixMagento2․2Di();
diff --git a/main/test/unit/Console/Command/ClearCommandTest.php b/main/test/unit/Console/Command/ClearCommandTest.php
new file mode 100644
index 0000000..4cc90f4
--- /dev/null
+++ b/main/test/unit/Console/Command/ClearCommandTest.php
@@ -0,0 +1,100 @@
+<?php
+
+namespace IntegerNet\Solr\Console\Command;
+
+use IntegerNet\Solr\Indexer\ProductIndexer;
+use IntegerNet\Solr\Model\Indexer;
+use Magento\Framework\App;
+use PHPUnit\Framework\Assert;
+use PHPUnit\Framework\TestCase;
+use Symfony\Component\Console\Input\ArrayInput;
+use Symfony\Component\Console\Output\BufferedOutput;
+
+class ClearCommandTest extends TestCase
+{
+    /**
+     * @var ClearCommand
+     */
+    private $command;
+
+    /**
+     * @var BufferedOutput
+     */
+    private $output;
+
+    /**
+     * @var Indexer\Console|\PHPUnit_Framework_MockObject_MockObject
+     */
+    private $indexer;
+
+    protected function setUp()
+    {
+        $this->indexer = $this->getMockBuilder(Indexer\Console::class)->disableOriginalConstructor()->getMock();
+        $appState = $this->getMockBuilder(App\State::class)->disableOriginalConstructor()->getMock();
+        $this->command = new ClearCommand($this->indexer, $appState);
+        $this->output = new BufferedOutput();
+    }
+
+
+    public function testClearsFullProductIndexWithoutArguments()
+    {
+        $this->indexer->expects($this->once())->method('clearStores')->with(null);
+        $exitCode = $this->runCommandWithInput([]);
+        $this->assertEquals(0, $exitCode, 'Exit code should be 0 for successful clear');
+        $this->assertOutputMessages('Clearing full Solr product index', 'Finished');
+    }
+
+    public function testClearProductIndexWithStoreFilter()
+    {
+        $storeIds = [1, 3, 'french'];
+        $this->indexer->expects($this->once())->method('clearStores')->with($storeIds);
+        $exitCode = $this->runCommandWithInput(
+            [
+                '--stores' => \implode(',', $storeIds),
+            ]
+        );
+        $this->assertEquals(0, $exitCode, 'Exit code should be 0 for successful clearing');
+        $this->assertOutputMessages('Clearing Solr product index for stores 1, 3, french', 'Finished');
+    }
+
+    public function testClearProductIndexOnSwappedCore()
+    {
+        $storeIds = [1];
+
+        $this->indexer->expects($this->once())->method('clearStoresOnSwappedCore')->with($storeIds);
+        $exitCode = $this->runCommandWithInput(
+            [
+                '--stores' => \implode(',', $storeIds),
+                '--useswapcore' => true,
+            ]
+        );
+        $this->assertEquals(0, $exitCode, 'Exit code should be 0 for successful clearing');
+        $this->assertOutputMessages(
+            'Clearing Solr product index for stores 1',
+            'Finished'
+        );
+    }
+
+    private function runCommandWithInput($input)
+    {
+        return $this->command->run(new ArrayInput($input), $this->output);
+    }
+
+    /**
+     * Assert that output contains all given strings.
+     *
+     * Note that this is only for output directly emitted from the command,
+     * not via progress updates because the indexer is mocked.
+     *
+     * @param string[] $messages
+     */
+    private function assertOutputMessages(...$messages)
+    {
+        $this->assertThat(
+            $this->output->fetch(),
+            $this->logicalAnd(
+                ...array_map([Assert::class, 'stringContains'], $messages)
+            )
+        );
+    }
+}
diff --git a/main/test/unit/Console/Command/ReindexCommandTest.php b/main/test/unit/Console/Command/ReindexCommandTest.php
index 9e11709..4630a61 100644
--- a/main/test/unit/Console/Command/ReindexCommandTest.php
+++ b/main/test/unit/Console/Command/ReindexCommandTest.php
@@ -23,7 +23,7 @@ class ReindexCommandTest extends TestCase
     private $output;
 
     /**
-     * @var ProductIndexer|\PHPUnit_Framework_MockObject_MockObject
+     * @var Indexer\Console|\PHPUnit_Framework_MockObject_MockObject
      */
     private $indexer;
 
diff --git a/main/test/unit/Console/Command/ReindexSliceCommandTest.php b/main/test/unit/Console/Command/ReindexSliceCommandTest.php
index 2bea2e5..eab6905 100644
--- a/main/test/unit/Console/Command/ReindexSliceCommandTest.php
+++ b/main/test/unit/Console/Command/ReindexSliceCommandTest.php
@@ -24,7 +24,7 @@ class ReindexSliceCommandTest extends TestCase
     private $output;
 
     /**
-     * @var ProductIndexer|\PHPUnit_Framework_MockObject_MockObject
+     * @var Indexer\Console|\PHPUnit_Framework_MockObject_MockObject
      */
     private $indexer;
 
diff --git a/main/test/unit/Console/Command/SwapCommandTest.php b/main/test/unit/Console/Command/SwapCommandTest.php
new file mode 100644
index 0000000..d6e5c19
--- /dev/null
+++ b/main/test/unit/Console/Command/SwapCommandTest.php
@@ -0,0 +1,82 @@
+<?php
+
+namespace IntegerNet\Solr\Console\Command;
+
+use IntegerNet\Solr\Indexer\ProductIndexer;
+use IntegerNet\Solr\Model\Indexer;
+use Magento\Framework\App;
+use PHPUnit\Framework\Assert;
+use PHPUnit\Framework\TestCase;
+use Symfony\Component\Console\Input\ArrayInput;
+use Symfony\Component\Console\Output\BufferedOutput;
+
+class SwapCommandTest extends TestCase
+{
+    /**
+     * @var SwapCommand
+     */
+    private $command;
+
+    /**
+     * @var BufferedOutput
+     */
+    private $output;
+
+    /**
+     * @var Indexer\Console|\PHPUnit_Framework_MockObject_MockObject
+     */
+    private $indexer;
+
+    protected function setUp()
+    {
+        $this->indexer = $this->getMockBuilder(Indexer\Console::class)->disableOriginalConstructor()->getMock();
+        $appState = $this->getMockBuilder(App\State::class)->disableOriginalConstructor()->getMock();
+        $this->command = new SwapCommand($this->indexer, $appState);
+        $this->output = new BufferedOutput();
+    }
+
+
+    public function testSwapAllCoresWithoutArguments()
+    {
+        $this->indexer->expects($this->once())->method('swapCores')->with(null);
+        $exitCode = $this->runCommandWithInput([]);
+        $this->assertEquals(0, $exitCode, 'Exit code should be 0 for successful clear');
+        $this->assertOutputMessages('Swap all cores', 'Finished');
+    }
+
+    public function testSwapCoresWithStoreFilter()
+    {
+        $storeIds = [1, 3, 'french'];
+        $this->indexer->expects($this->once())->method('swapCores')->with($storeIds);
+        $exitCode = $this->runCommandWithInput(
+            [
+                '--stores' => \implode(',', $storeIds),
+            ]
+        );
+        $this->assertEquals(0, $exitCode, 'Exit code should be 0 for successful clearing');
+        $this->assertOutputMessages('Swap cores for stores 1, 3, french', 'Finished');
+    }
+
+    private function runCommandWithInput($input)
+    {
+        return $this->command->run(new ArrayInput($input), $this->output);
+    }
+
+    /**
+     * Assert that output contains all given strings.
+     *
+     * Note that this is only for output directly emitted from the command,
+     * not via progress updates because the indexer is mocked.
+     *
+     * @param string[] $messages
+     */
+    private function assertOutputMessages(...$messages)
+    {
+        $this->assertThat(
+            $this->output->fetch(),
+            $this->logicalAnd(
+                ...array_map([Assert::class, 'stringContains'], $messages)
+            )
+        );
+    }
+}