diff --git a/src/Inspector/ApplicationState.php b/src/Inspector/ApplicationState.php
index 9996b20..1b73fd2 100644
--- a/src/Inspector/ApplicationState.php
+++ b/src/Inspector/ApplicationState.php
@@ -4,7 +4,10 @@
 
 namespace Yiisoft\Yii\Debug\Api\Inspector;
 
-class ApplicationState
+/**
+ * @internal
+ */
+final class ApplicationState
 {
-    public static $params;
+    public static array $params = [];
 }
diff --git a/tests/Support/Application/fail.sh b/tests/Support/Application/fail.sh
new file mode 100644
index 0000000..4bbf6fa
--- /dev/null
+++ b/tests/Support/Application/fail.sh
@@ -0,0 +1,2 @@
+echo 'failed'
+exit $1
diff --git a/tests/Unit/Inspector/ApplicationStateTest.php b/tests/Unit/Inspector/ApplicationStateTest.php
new file mode 100644
index 0000000..2b8aed5
--- /dev/null
+++ b/tests/Unit/Inspector/ApplicationStateTest.php
@@ -0,0 +1,19 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Yiisoft\Yii\Debug\Api\Tests\Unit\Inspector;
+
+use PHPUnit\Framework\TestCase;
+use Yiisoft\Yii\Debug\Api\Inspector\ApplicationState;
+
+final class ApplicationStateTest extends TestCase
+{
+    public function testStatus(): void
+    {
+        $this->assertEquals([], ApplicationState::$params);
+
+        ApplicationState::$params = ['key' => 'value'];
+        $this->assertEquals(['key' => 'value'], ApplicationState::$params);
+    }
+}
diff --git a/tests/Unit/Inspector/Command/BashCommandTest.php b/tests/Unit/Inspector/Command/BashCommandTest.php
new file mode 100644
index 0000000..013da82
--- /dev/null
+++ b/tests/Unit/Inspector/Command/BashCommandTest.php
@@ -0,0 +1,41 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Yiisoft\Yii\Debug\Api\Tests\Unit\Inspector\Command;
+
+use PHPUnit\Framework\TestCase;
+use Yiisoft\Aliases\Aliases;
+use Yiisoft\Yii\Debug\Api\Inspector\Command\BashCommand;
+use Yiisoft\Yii\Debug\Api\Inspector\CommandResponse;
+
+final class BashCommandTest extends TestCase
+{
+    public function testSuccess(): void
+    {
+        $aliases = new Aliases([
+            '@root' => __DIR__,
+        ]);
+        $command = new BashCommand($aliases, ['echo', 'test']);
+
+        $response = $command->run();
+
+        $this->assertSame(CommandResponse::STATUS_OK, $response->getStatus());
+        $this->assertSame('test' . PHP_EOL, $response->getResult());
+        $this->assertSame([], $response->getErrors());
+    }
+
+    public function testError(): void
+    {
+        $aliases = new Aliases([
+            '@root' => dirname(__DIR__, 3) . '/Support/Application',
+        ]);
+        $command = new BashCommand($aliases, ['bash', 'fail.sh', '1']);
+
+        $response = $command->run();
+
+        $this->assertSame(CommandResponse::STATUS_ERROR, $response->getStatus());
+        $this->assertSame('failed' . PHP_EOL, $response->getResult());
+        $this->assertSame([], $response->getErrors());
+    }
+}
diff --git a/tests/Unit/Inspector/CommandResponseTest.php b/tests/Unit/Inspector/CommandResponseTest.php
new file mode 100644
index 0000000..68b6428
--- /dev/null
+++ b/tests/Unit/Inspector/CommandResponseTest.php
@@ -0,0 +1,20 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Yiisoft\Yii\Debug\Api\Tests\Unit\Inspector;
+
+use PHPUnit\Framework\TestCase;
+use Yiisoft\Yii\Debug\Api\Inspector\CommandResponse;
+
+final class CommandResponseTest extends TestCase
+{
+    public function testStatus(): void
+    {
+        $response = new CommandResponse(CommandResponse::STATUS_OK, 'result', ['errors']);
+
+        $this->assertSame(CommandResponse::STATUS_OK, $response->getStatus());
+        $this->assertSame('result', $response->getResult());
+        $this->assertSame(['errors'], $response->getErrors());
+    }
+}
diff --git a/tests/Inspector/Database/DbSchemaProviderTest.php b/tests/Unit/Inspector/Database/DbSchemaProviderTest.php
similarity index 98%
rename from tests/Inspector/Database/DbSchemaProviderTest.php
rename to tests/Unit/Inspector/Database/DbSchemaProviderTest.php
index 0584e09..5a00506 100644
--- a/tests/Inspector/Database/DbSchemaProviderTest.php
+++ b/tests/Unit/Inspector/Database/DbSchemaProviderTest.php
@@ -2,7 +2,7 @@
 
 declare(strict_types=1);
 
-namespace Yiisoft\Yii\Debug\Api\Tests\Inspector\Database;
+namespace Yiisoft\Yii\Debug\Api\Tests\Unit\Inspector\Database;
 
 use PHPUnit\Framework\TestCase;
 use Yiisoft\Cache\NullCache;