MINOR: Add tests for some search-form fixes

These 2 tests validate that the following bugs have been fixed.

https://github.com/silverstripe/silverstripe-framework/issues/3212
https://github.com/silverstripe/silverstripe-cms/issues/1452

tests/php/Search/DatabaseSearchEngineTest.php

@@ -0,0 +1,65 @@
+<?php
+
+namespace SilverStripe\CMS\Tests\Search;
+
+use SilverStripe\Dev\SapphireTest;
+use SilverStripe\CMS\Model\SiteTree;
+use SilverStripe\Assets\File;
+use SilverStripe\ORM\DB;
+use SilverStripe\Core\Config\Config;
+use SilverStripe\ORM\Search\FulltextSearchable;
+
+class DatabaseSearchEngineTest extends SapphireTest
+{
+    protected $usesDatabase = true;
+
+    public static function setUpBeforeClass()
+    {
+        parent::setUpBeforeClass();
+
+        // Postgres doesn't refresh TSearch indexes when the schema changes after CREATE TABLE
+        // MySQL will need a different table type
+        if (static::$tempDB) {
+            static::$tempDB->kill();
+            Config::modify();
+        }
+        FulltextSearchable::enable();
+        static::$tempDB->build();
+        static::resetDBSchema(true);
+    }
+
+    /**
+     * Validate that https://github.com/silverstripe/silverstripe-cms/issues/3212 is fixed
+     */
+    public function testSearchEngineEscapeAs()
+    {
+        $page = new SiteTree();
+        $page->Title = "This page provides food as bar";
+        $page->write();
+        $page->doPublish();
+
+        $results = DB::get_conn()->searchEngine([ SiteTree::class, File::class ], "foo* as* bar*", 0, 100, "\"Relevance\" DESC", "", true);
+
+        $this->assertCount(1, $results);
+        $this->assertEquals(
+            "This page provides food as bar",
+            $results->First()->Title
+        );
+    }
+
+    /**
+     * Validate that https://github.com/silverstripe/silverstripe-cms/issues/1452 is fixed
+     */
+    public function testSearchEngineEscapeGreaterThan()
+    {
+        $page = new SiteTree();
+        $page->Title = "Unrelated page";
+        $page->write();
+        $page->doPublish();
+
+        $results = DB::get_conn()->searchEngine([ SiteTree::class, File::class ], "foo>*", 0, 100, "\"Relevance\" DESC", "", true);
+
+        // We're not trying to match this query, just confirm that it successfully executes
+        $this->assertCount(0, $results);
+    }
+}