Tests: Add tests for wpdb::_real_escape().

Adds a new dedicated test file.

Adds a test to check that various input types passed to `wpdb::_real_escape()` are handled correctly.

Note: This new test does not test the actual escaping or other logic in the function. Rather, it just and only tests and documents how the function handles various input types.

Props jrf, hellofromTonya.
See #53363.

git-svn-id: https://develop.svn.wordpress.org/trunk@51798 602fd350-edb4-49c9-b593-d223f7449a82

tests/phpunit/tests/db/realEscape.php

@@ -0,0 +1,87 @@
+<?php
+
+/**
+ * Test WPDB _real_escape() method.
+ *
+ * @group  wpdb
+ * @covers wpdb::_real_escape
+ */
+class Tests_DB_RealEscape extends WP_UnitTestCase {
+
+	/**
+	 * Test that various types of input passed to `wpdb::_real_escape()` are handled correctly.
+	 *
+	 * Note: this test does not test the actual escaping or other logic in the function.
+	 * It just and only tests and documents how the function handles various input types.
+	 *
+	 * @ticket 53635
+	 *
+	 * @dataProvider data_real_escape_input_type_handling
+	 *
+	 * @param mixed  $input    The input to escape.
+	 * @param string $expected The expected function output.
+	 */
+	function test_real_escape_input_type_handling( $input, $expected ) {
+		global $wpdb;
+
+		$this->assertSame( $expected, $wpdb->_real_escape( $input ) );
+	}
+
+	/**
+	 * Data provider.
+	 *
+	 * @var array
+	 */
+	public function data_real_escape_input_type_handling() {
+		return array(
+			'null'             => array(
+				'input'    => null,
+				'expected' => '',
+			),
+			'boolean false'    => array(
+				'input'    => false,
+				'expected' => '',
+			),
+			'boolean true'     => array(
+				'input'    => true,
+				'expected' => '1',
+			),
+			'integer zero'     => array(
+				'input'    => 0,
+				'expected' => '0',
+			),
+			'negative integer' => array(
+				'input'    => -1327,
+				'expected' => '-1327',
+			),
+			'positive integer' => array(
+				'input'    => 47896,
+				'expected' => '47896',
+			),
+			'float zero'       => array(
+				'input'    => 0.0,
+				'expected' => '0',
+			),
+			'positive float'   => array(
+				'input'    => 25.52,
+				'expected' => '25.52',
+			),
+			'simple string'    => array(
+				'input'    => 'foobar',
+				'expected' => 'foobar',
+			),
+			'empty array'      => array(
+				'input'    => array(),
+				'expected' => '',
+			),
+			'non-empty array'  => array(
+				'input'    => array( 1, 2, 3 ),
+				'expected' => '',
+			),
+			'simple object'    => array(
+				'input'    => new stdClass(),
+				'expected' => '',
+			),
+		);
+	}
+}