diff --git a/src/Client/GroupsClient.php b/src/Client/GroupsClient.php
index 96ea459..06d7f18 100644
--- a/src/Client/GroupsClient.php
+++ b/src/Client/GroupsClient.php
@@ -35,32 +35,23 @@ class GroupsClient extends Client implements ClientInterface
     public const ACTION_LIST_GROUPS = 'list';
 
     /**
-     * @param string $action Action that client performs
+     * @param self::ACTION_* $action Action that client performs
      */
     public function __construct(
         private readonly Group $group,
         private readonly string $action,
     ) {
-        if (!$this->isActionValid($action)) {
-            throw new InvalidArgumentException('Action argument provided to construct method is invalid.');
-        }
+        $this->validateAction($action);
     }
 
     public function buildApiUrl(): string
     {
-        if ($this->action === self::ACTION_CREATE_GROUP) {
-            return Curl::API_BASE_URL.'/'.Curl::API_VERSION.'/groups.json';
-        }
-
-        if ($this->action === self::ACTION_LIST_GROUPS) {
-            return Curl::API_BASE_URL.'/'.Curl::API_VERSION.'/groups.json?token='.$this->group->getApplication()->getToken();
-        }
-
-        if ($this->action === self::ACTION_RETRIEVE_GROUP) {
-            return Curl::API_BASE_URL.'/'.Curl::API_VERSION.'/groups/'.$this->group->getKey().'.json?token='.$this->group->getApplication()->getToken();
-        }
-
-        return Curl::API_BASE_URL.'/'.Curl::API_VERSION.'/groups/'.$this->group->getKey().'/'.$this->action.'.json?token='.$this->group->getApplication()->getToken();
+        return match ($this->action) {
+            self::ACTION_CREATE_GROUP => sprintf('%s/%s/groups.json', Curl::API_BASE_URL, Curl::API_VERSION),
+            self::ACTION_LIST_GROUPS => sprintf('%s/%s/groups.json?token=%s', Curl::API_BASE_URL, Curl::API_VERSION, $this->group->getApplication()->getToken()),
+            self::ACTION_RETRIEVE_GROUP => sprintf('%s/%s/groups/%s.json?token=%s', Curl::API_BASE_URL, Curl::API_VERSION, $this->group->getKey(), $this->group->getApplication()->getToken()),
+            default => sprintf('%s/%s/groups/%s/%s.json?token=%s', Curl::API_BASE_URL, Curl::API_VERSION, $this->group->getKey(), $this->action, $this->group->getApplication()->getToken()),
+        };
     }
 
     /**
@@ -72,28 +63,25 @@ public function buildCurlPostFields(?Recipient $recipient = null): array
             'token' => $this->group->getApplication()->getToken(),
         ];
 
-        if (
-            $this->action === self::ACTION_ADD_USER
-            || $this->action === self::ACTION_REMOVE_USER
-            || $this->action === self::ACTION_DISABLE_USER
-            || $this->action === self::ACTION_ENABLE_USER
-        ) {
+        if (\in_array($this->action, [self::ACTION_ADD_USER, self::ACTION_REMOVE_USER, self::ACTION_DISABLE_USER, self::ACTION_ENABLE_USER], true)) {
+            if (!$recipient instanceof Recipient) {
+                throw new \LogicException('Recipient object must be provided for this action.');
+            }
+
             $curlPostFields['user'] = $recipient->getUserKey();
-        }
 
-        if ($this->action === self::ACTION_ADD_USER) {
-            if (!empty($recipient->getDevice())) {
-                $curlPostFields['device'] = $recipient->getDevice()[0];
-            }
+            if ($this->action === self::ACTION_ADD_USER) {
+                if (!empty($recipient->getDevice())) {
+                    $curlPostFields['device'] = $recipient->getDevice()[0];
+                }
 
-            if (null !== $recipient->getMemo()) {
-                $curlPostFields['memo'] = $recipient->getMemo();
+                if (null !== $recipient->getMemo()) {
+                    $curlPostFields['memo'] = $recipient->getMemo();
+                }
             }
         }
 
-        if ($this->action === self::ACTION_RENAME_GROUP
-            || $this->action === self::ACTION_CREATE_GROUP
-        ) {
+        if (\in_array($this->action, [self::ACTION_RENAME_GROUP, self::ACTION_CREATE_GROUP], true)) {
             $curlPostFields['name'] = $this->group->getName();
         }
 
@@ -103,14 +91,12 @@ public function buildCurlPostFields(?Recipient $recipient = null): array
     /**
      * Checks if action that was provided into construct is valid.
      */
-    private function isActionValid(string $action): bool
+    private function validateAction(string $action): void
     {
         $oClass = new \ReflectionClass(self::class);
 
-        if (\in_array($action, $oClass->getConstants(), true)) {
-            return true;
+        if (!\in_array($action, $oClass->getConstants(), true)) {
+            throw new InvalidArgumentException('Action argument provided to construct method is invalid.');
         }
-
-        return false;
     }
 }
diff --git a/tests/Client/GroupsClientTest.php b/tests/Client/GroupsClientTest.php
index a2cca0f..b256489 100644
--- a/tests/Client/GroupsClientTest.php
+++ b/tests/Client/GroupsClientTest.php
@@ -34,69 +34,104 @@ public function testCanBeConstructed(): void
         $this->assertInstanceOf(GroupsClient::class, $client);
     }
 
-    public function testBuildApiUrl(): void
+    /**
+     * @dataProvider buildApiUrlProvider
+     */
+    public function testBuildApiUrl(string $expected, string $action): void
     {
         $application = new Application('cccc3333CCCC3333dddd4444DDDD44'); // using dummy token
         $group = new Group('eeee5555EEEE5555ffff6666FFFF66', $application); // using dummy group key
 
-        // testing various "actions" below
-
-        $client = new GroupsClient($group, GroupsClient::ACTION_RETRIEVE_GROUP);
-        $this->assertEquals('https://api.pushover.net/1/groups/eeee5555EEEE5555ffff6666FFFF66.json?token=cccc3333CCCC3333dddd4444DDDD44', $client->buildApiUrl());
-
-        $client = new GroupsClient($group, GroupsClient::ACTION_ADD_USER);
-        $this->assertEquals('https://api.pushover.net/1/groups/eeee5555EEEE5555ffff6666FFFF66/add_user.json?token=cccc3333CCCC3333dddd4444DDDD44', $client->buildApiUrl());
+        $client = new GroupsClient($group, $action);
+        $this->assertSame($expected, $client->buildApiUrl());
+    }
 
-        $client = new GroupsClient($group, GroupsClient::ACTION_LIST_GROUPS);
-        $this->assertSame('https://api.pushover.net/1/groups.json?token=cccc3333CCCC3333dddd4444DDDD44', $client->buildApiUrl());
+    /**
+     * @return iterable<array{string, string}>
+     */
+    public static function buildApiUrlProvider(): iterable
+    {
+        yield [
+            'https://api.pushover.net/1/groups/eeee5555EEEE5555ffff6666FFFF66.json?token=cccc3333CCCC3333dddd4444DDDD44',
+            GroupsClient::ACTION_RETRIEVE_GROUP,
+        ];
+
+        yield [
+            'https://api.pushover.net/1/groups/eeee5555EEEE5555ffff6666FFFF66/add_user.json?token=cccc3333CCCC3333dddd4444DDDD44',
+            GroupsClient::ACTION_ADD_USER,
+        ];
+
+        yield [
+            'https://api.pushover.net/1/groups.json?token=cccc3333CCCC3333dddd4444DDDD44',
+            GroupsClient::ACTION_LIST_GROUPS,
+        ];
     }
 
-    public function testBuildCurlPostFields(): void
+    /**
+     * @dataProvider buildCurlPostFieldsProvider
+     *
+     * @param array<string, string> $expected
+     */
+    public function testBuildCurlPostFields(array $expected, string $action): void
     {
         $application = new Application('cccc3333CCCC3333dddd4444DDDD44'); // using dummy token
         $group = new Group('eeee5555EEEE5555ffff6666FFFF66', $application); // using dummy group key
         $recipient = new Recipient('aaaa1111AAAA1111bbbb2222BBBB22'); // using dummy user key
 
-        // testing various "actions" below
+        $client = new GroupsClient($group, $action);
 
-        $client = new GroupsClient($group, GroupsClient::ACTION_ADD_USER);
-
-        $this->assertEquals(
-            [
-                'token' => 'cccc3333CCCC3333dddd4444DDDD44',
-                'user' => 'aaaa1111AAAA1111bbbb2222BBBB22',
-            ],
+        $this->assertSame(
+            $expected,
             $client->buildCurlPostFields($recipient),
         );
+    }
 
-        $client = new GroupsClient($group, GroupsClient::ACTION_REMOVE_USER);
+    /**
+     * @return iterable<array{array<string, string>, string}>
+     */
+    public static function buildCurlPostFieldsProvider(): iterable
+    {
+        $base = [
+            'token' => 'cccc3333CCCC3333dddd4444DDDD44',
+            'user' => 'aaaa1111AAAA1111bbbb2222BBBB22',
+        ];
+
+        foreach ([
+            GroupsClient::ACTION_ADD_USER,
+            GroupsClient::ACTION_REMOVE_USER,
+            GroupsClient::ACTION_ENABLE_USER,
+            GroupsClient::ACTION_DISABLE_USER,
+        ] as $action) {
+            yield [$base, $action];
+        }
+    }
 
-        $this->assertEquals(
-            [
-                'token' => 'cccc3333CCCC3333dddd4444DDDD44',
-                'user' => 'aaaa1111AAAA1111bbbb2222BBBB22',
-            ],
-            $client->buildCurlPostFields($recipient),
-        );
+    /**
+     * @dataProvider actionsNeedRecipientProvider
+     */
+    public function testBuildCurlPostFieldsThrowsExceptionWhenRecipientIsNotProvided(string $action): void
+    {
+        $application = new Application('cccc3333CCCC3333dddd4444DDDD44'); // using dummy token
+        $group = new Group('eeee5555EEEE5555ffff6666FFFF66', $application); // using dummy group key
 
-        $client = new GroupsClient($group, GroupsClient::ACTION_ENABLE_USER);
+        $client = new GroupsClient($group, $action);
 
-        $this->assertEquals(
-            [
-                'token' => 'cccc3333CCCC3333dddd4444DDDD44',
-                'user' => 'aaaa1111AAAA1111bbbb2222BBBB22',
-            ],
-            $client->buildCurlPostFields($recipient),
-        );
+        $this->expectException(\LogicException::class);
+        $this->expectExceptionMessage('Recipient object must be provided for this action.');
 
-        $client = new GroupsClient($group, GroupsClient::ACTION_DISABLE_USER);
+        $client->buildCurlPostFields();
+    }
 
-        $this->assertEquals(
-            [
-                'token' => 'cccc3333CCCC3333dddd4444DDDD44',
-                'user' => 'aaaa1111AAAA1111bbbb2222BBBB22',
-            ],
-            $client->buildCurlPostFields($recipient),
-        );
+    /**
+     * @return iterable<list<string>>
+     */
+    public static function actionsNeedRecipientProvider(): iterable
+    {
+        return [
+            [GroupsClient::ACTION_ADD_USER],
+            [GroupsClient::ACTION_REMOVE_USER],
+            [GroupsClient::ACTION_ENABLE_USER],
+            [GroupsClient::ACTION_DISABLE_USER],
+        ];
     }
 }