diff --git a/src/wp-admin/includes/misc.php b/src/wp-admin/includes/misc.php
index 3724684ffd428..61e9a09e2b799 100644
--- a/src/wp-admin/includes/misc.php
+++ b/src/wp-admin/includes/misc.php
@@ -833,7 +833,6 @@ function iis7_rewrite_rule_exists( $filename ) {
 	}
 
 	$doc = new DOMDocument();
-
 	if ( $doc->load( $filename ) === false ) {
 		return false;
 	}
diff --git a/tests/phpunit/tests/admin/includes/misc/iis7RewriteRuleExists.php b/tests/phpunit/tests/admin/includes/misc/iis7RewriteRuleExists.php
new file mode 100644
index 0000000000000..83532b1f51983
--- /dev/null
+++ b/tests/phpunit/tests/admin/includes/misc/iis7RewriteRuleExists.php
@@ -0,0 +1,100 @@
+<?php
+
+/**
+ * Tests for the iis7_rewrite_rule_exists() function.
+ *
+ * @group admin
+ *
+ * @covers ::iis7_rewrite_rule_exists
+ */
+class Tests_iis7_rewrite_rule_exists extends WP_UnitTestCase {
+
+	/**
+	 * Path to the temporary file.
+	 *
+	 * @var string
+	 */
+	private $temp_file;
+
+	public function set_up() {
+		parent::set_up();
+
+		require_once ABSPATH . 'wp-admin/includes/misc.php';
+
+		$this->temp_file = wp_tempnam( 'web.config' );
+	}
+
+	public function tear_down() {
+		if ( file_exists( $this->temp_file ) ) {
+			unlink( $this->temp_file );
+		}
+
+		parent::tear_down();
+	}
+
+	/**
+	 * Tests that iis7_rewrite_rule_exists() correctly identifies the existence of rules.
+	 *
+	 * @ticket 65148
+	 *
+	 * @dataProvider data_iis7_rewrite_rule_exists
+	 *
+	 * @phpstan-return array<string, array{expected: bool, content: string}>
+	 *
+	 * @param bool   $expected Whether the rule is expected to exist.
+	 * @param string $content  The XML content of the file.
+	 */
+	public function test_iis7_rewrite_rule_exists( $expected, $content ) {
+		if ( 'Not XML' === $content ) {
+			file_put_contents( $this->temp_file, $content );
+			// phpcs:ignore WordPress.PHP.NoSilencedErrors.Discouraged
+			$this->assertSame( $expected, @iis7_rewrite_rule_exists( $this->temp_file ) );
+		} else {
+			file_put_contents( $this->temp_file, $content );
+			$this->assertSame( $expected, iis7_rewrite_rule_exists( $this->temp_file ) );
+		}
+	}
+
+	/**
+	 * Data provider for test_iis7_rewrite_rule_exists.
+	 *
+	 * @return array<string, array{expected: bool, content: string}>
+	 */
+	public function data_iis7_rewrite_rule_exists(): array {
+		return array(
+			'Rule with name starting with "wordpress" exists' => array(
+				'expected' => true,
+				'content'  => '<configuration><system.webServer><rewrite><rules><rule name="wordpress-rules" /></rules></rewrite></system.webServer></configuration>',
+			),
+			'Rule with name "wordpress" exists' => array(
+				'expected' => true,
+				'content'  => '<configuration><system.webServer><rewrite><rules><rule name="wordpress" /></rules></rewrite></system.webServer></configuration>',
+			),
+			'Rule with name "WordPress" exists' => array(
+				'expected' => true,
+				'content'  => '<configuration><system.webServer><rewrite><rules><rule name="WordPress" /></rules></rewrite></system.webServer></configuration>',
+			),
+			'Rule does not exist'               => array(
+				'expected' => false,
+				'content'  => '<configuration><system.webServer><rewrite><rules><rule name="other-rule" /></rules></rewrite></system.webServer></configuration>',
+			),
+			'Empty configuration'               => array(
+				'expected' => false,
+				'content'  => '<configuration />',
+			),
+			'Invalid XML'                       => array(
+				'expected' => false,
+				'content'  => 'Not XML',
+			),
+		);
+	}
+
+	/**
+	 * Tests that iis7_rewrite_rule_exists() returns false if the file does not exist.
+	 *
+	 * @ticket 65148
+	 */
+	public function test_iis7_rewrite_rule_exists_non_existent_file() {
+		$this->assertFalse( iis7_rewrite_rule_exists( '/non/existent/file' ) );
+	}
+}