Check that two files are the same by comparing the fid and filepath.
$file1: File object to compare.
$file2: File object to compare.
function assertSameFile($file1, $file2) {
$this
->assertEqual($file1->fid, $file2->fid, t('Files have the same ids: %file1 == %file2.', array(
'%file1' => $file1->fid,
'%file2-fid' => $file2->fid,
)), 'Same file');
$this
->assertEqual($file1->uri, $file2->uri, t('Files have the same path: %file1 == %file2.', array(
'%file1' => $file1->uri,
'%file2' => $file2->uri,
)), 'Same file');
}