public function testKeyCache()
{
$path = null;
$pool = new CachePool(['idx_1', 'idx_2', 'idx_3']);
$result = $pool->exposeGetHierarchyKey('|foo', $path);
$this->assertEqualsSha1('root!!idx_1!foo!!idx_2!', $result);
$this->assertEqualsSha1('path!root!!idx_1!foo!', $path);
// Make sure re reuse the old index value we already looked up for 'root'.
$result = $pool->exposeGetHierarchyKey('|bar', $path);
$this->assertEqualsSha1('root!!idx_1!bar!!idx_3!', $result);
$this->assertEqualsSha1('path!root!!idx_1!bar!', $path);
}