diff --git a/tests/phpunit/tests/admin/includes/ajax-actions/inlineSaveTax.php b/tests/phpunit/tests/admin/includes/ajax-actions/inlineSaveTax.php
new file mode 100644
index 0000000000000..1ee7a44093358
--- /dev/null
+++ b/tests/phpunit/tests/admin/includes/ajax-actions/inlineSaveTax.php
@@ -0,0 +1,158 @@
+<?php
+
+/**
+ * Admin Ajax functions to be tested.
+ */
+require_once ABSPATH . 'wp-admin/includes/ajax-actions.php';
+
+/**
+ * Testing wp_ajax_inline_save_tax() functionality.
+ *
+ * @package WordPress
+ * @subpackage UnitTests
+ * @since 3.1.0
+ *
+ * @group ajax
+ *
+ * @covers ::wp_ajax_inline_save_tax
+ */
+class Tests_wp_ajax_inline_save_tax extends WP_Ajax_UnitTestCase {
+
+	/**
+	 * Administrator user ID.
+	 *
+	 * @var int
+	 */
+	protected static $admin_id;
+
+	/**
+	 * Setup test fixtures.
+	 *
+	 * @param WP_UnitTest_Factory $factory
+	 */
+	public static function wpSetUpBeforeClass( WP_UnitTest_Factory $factory ): void {
+		self::$admin_id = $factory->user->create( array( 'role' => 'administrator' ) );
+	}
+
+	/**
+	 * Tests successful term update via Quick Edit.
+	 *
+	 * @ticket 65252
+	 */
+	public function test_inline_save_tax_success(): void {
+		wp_set_current_user( self::$admin_id );
+
+		$term_id = self::factory()->term->create(
+			array(
+				'taxonomy' => 'category',
+				'name'     => 'Initial Name',
+				'slug'     => 'initial-slug',
+			)
+		);
+
+		$_POST = array(
+			'action'       => 'inline-save-tax',
+			'taxonomy'     => 'category',
+			'tax_ID'       => $term_id,
+			'name'         => 'Updated Name',
+			'slug'         => 'updated-slug',
+			'_inline_edit' => wp_create_nonce( 'taxinlineeditnonce' ),
+		);
+
+		try {
+			$this->_handleAjax( 'inline-save-tax' );
+		} catch ( WPAjaxDieContinueException $e ) {
+			// Expect success.
+		}
+
+		$term = get_term( $term_id, 'category' );
+		$this->assertSame( 'Updated Name', $term->name );
+		$this->assertSame( 'updated-slug', $term->slug );
+		$this->assertStringContainsString( 'Updated Name', $this->_last_response );
+	}
+
+	/**
+	 * Tests failure due to invalid nonce.
+	 *
+	 * @ticket 65252
+	 */
+	public function test_inline_save_tax_invalid_nonce(): void {
+		wp_set_current_user( self::$admin_id );
+
+		$_POST = array(
+			'action'       => 'inline-save-tax',
+			'taxonomy'     => 'category',
+			'tax_ID'       => 1,
+			'_inline_edit' => 'invalid-nonce',
+		);
+
+		$this->expectException( WPAjaxDieContinueException::class );
+		$this->expectExceptionMessage( '-1' );
+
+		$this->_handleAjax( 'inline-save-tax' );
+	}
+
+	/**
+	 * Tests failure due to invalid taxonomy.
+	 *
+	 * @ticket 65252
+	 */
+	public function test_inline_save_tax_invalid_taxonomy(): void {
+		wp_set_current_user( self::$admin_id );
+
+		$_POST = array(
+			'action'       => 'inline-save-tax',
+			'taxonomy'     => 'non_existent_taxonomy',
+			'_inline_edit' => wp_create_nonce( 'taxinlineeditnonce' ),
+		);
+
+		$this->expectException( WPAjaxDieContinueException::class );
+		$this->expectExceptionMessage( '0' );
+
+		$this->_handleAjax( 'inline-save-tax' );
+	}
+
+	/**
+	 * Tests failure due to missing tax_ID.
+	 *
+	 * @ticket 65252
+	 */
+	public function test_inline_save_tax_missing_tax_id(): void {
+		wp_set_current_user( self::$admin_id );
+
+		$_POST = array(
+			'action'       => 'inline-save-tax',
+			'taxonomy'     => 'category',
+			'_inline_edit' => wp_create_nonce( 'taxinlineeditnonce' ),
+		);
+
+		$this->expectException( WPAjaxDieContinueException::class );
+		$this->expectExceptionMessage( '-1' );
+
+		$this->_handleAjax( 'inline-save-tax' );
+	}
+
+	/**
+	 * Tests failure due to insufficient permissions.
+	 *
+	 * @ticket 65252
+	 */
+	public function test_inline_save_tax_insufficient_permissions(): void {
+		$user_id = self::factory()->user->create( array( 'role' => 'subscriber' ) );
+		wp_set_current_user( $user_id );
+
+		$term_id = self::factory()->term->create( array( 'taxonomy' => 'category' ) );
+
+		$_POST = array(
+			'action'       => 'inline-save-tax',
+			'taxonomy'     => 'category',
+			'tax_ID'       => $term_id,
+			'_inline_edit' => wp_create_nonce( 'taxinlineeditnonce' ),
+		);
+
+		$this->expectException( WPAjaxDieContinueException::class );
+		$this->expectExceptionMessage( '-1' );
+
+		$this->_handleAjax( 'inline-save-tax' );
+	}
+}