Add unit tests for wp_is_valid_last_changed function

Introduce PHPUnit tests to validate the behavior of the wp_is_valid_last_changed function. Tests cover various scenarios, including valid usage, missing or mismatched timestamps, and invalid input types. These additions ensure robustness and prevent potential regressions.

Author: spacedmonkey

tests/phpunit/tests/functions/wpIsValidLastChanged.php

@@ -0,0 +1,55 @@
+<?php
+
+/**
+ * @group functions
+ *
+ * @covers ::wp_is_valid_last_changed
+ */
+class Tests_Functions_wpIsValidLastChanged extends WP_UnitTestCase {
+
+	public function test_wp_is_valid_last_changed() {
+		$last_changed = microtime();
+		$cache_value  = array(
+			'last_changed' => $last_changed,
+			'value'        => 'test_value',
+		);
+		$this->assertTrue( wp_is_valid_last_changed( $cache_value, $last_changed ) );
+	}
+
+	public function test_wp_is_valid_last_changed_no_last_chaned() {
+		$last_changed = microtime();
+		$cache_value  = array(
+			'value' => 'test_value',
+		);
+		$this->assertFalse( wp_is_valid_last_changed( $cache_value, $last_changed ) );
+	}
+
+	public function test_wp_is_valid_last_changed_different_last_chaned() {
+		$last_changed = microtime();
+		$cache_value  = array(
+			'last_changed' => 444444,
+			'value'        => 'test_value',
+		);
+		$this->assertFalse( wp_is_valid_last_changed( $cache_value, $last_changed ) );
+	}
+
+	/**
+	 * @dataProvider data_invalid_values
+	 */
+	public function test_wp_is_valid_last_changed_invalid_values( $value ) {
+		$this->assertFalse( wp_is_valid_last_changed( $value, '' ) );
+	}
+
+	public function data_invalid_values() {
+		return array(
+			'empty'    => array( '' ),
+			'null'     => array( null ),
+			'number 0' => array( 0 ),
+			'number 1' => array( 1 ),
+			'false'    => array( false ),
+			'true'     => array( true ),
+			'array'    => array( array() ),
+			'object'   => array( new stdClass() ),
+		);
+	}
+}