Add validation for incorrect config data

src/Config.php

@@ -4,6 +4,8 @@ declare(strict_types=1);
 
 namespace Opdavies\Glassboxx;
 
+use Assert\Assert;
+
 class Config
 {
     /** @var int $vendorId */
@@ -20,6 +22,12 @@ class Config
         string $username,
         string $password
     ) {
+        Assert::that($vendorId)
+            ->greaterOrEqualThan(1, 'Vendor ID cannot be a negative number');
+
+        Assert::that($username)->notEmpty('Username cannot be empty');
+        Assert::that($password)->notEmpty('Password cannot be empty');
+
         $this->password = $password;
         $this->username = $username;
         $this->vendorId = $vendorId;

tests/ConfigTest.php

@@ -4,6 +4,7 @@ declare(strict_types=1);
 
 namespace Opdavies\Glassboxx\Tests;
 
+use Assert\AssertionFailedException;
 use Opdavies\Glassboxx\Config;
 use PHPUnit\Framework\TestCase;
 
@@ -21,4 +22,49 @@ class ConfigTest extends TestCase
         $this->assertSame('opdavies', $config->getUsername());
         $this->assertSame('secret', $config->getPassword());
     }
+
+    public function badCreateDataProvider(): array
+    {
+        return [
+            'Negative vendor ID' => [
+                'vendor id' => -1,
+                'username' => 'user',
+                'password' => 'secret',
+                'message' => 'Vendor ID cannot be a negative number',
+            ],
+            'Username is an empty string' => [
+                'vendor id' => 123,
+                'username' => '',
+                'password' => 'secret',
+                'message' => 'Username cannot be empty',
+            ],
+            'Password is an empty string' => [
+                'vendor id' => 123,
+                'username' => 'user',
+                'password' => '',
+                'message' => 'Password cannot be empty',
+            ],
+        ];
+    }
+
+    /**
+     * @dataProvider badCreateDataProvider
+     *
+     * @param int $vendorId
+     * @param string $username
+     * @param string $password
+     * @param string $message
+     */
+    public function testThatAnExceptionIsThrownWhenBadData(
+        int $vendorId,
+        string $username,
+        string $password,
+        string $message
+    ) {
+        $this->expectException(AssertionFailedException::class);
+        $this->expectExceptionMessage($message);
+
+        new Config($vendorId, $username, $password);
+    }
+
 }