You can use Shortest
if the sub-strings of the form <td, class=test, >...</td>
don't contain nested sub-strings of the form <td, class=test, >
or </td>
. If they do, follow this linkthis link.
v = "...<td, class=test, >strings1</td>...<td, class=test, >strings2</td>..";
StringCases[v, Shortest["<td, class=test, >" ~~ x__ ~~ "</td>"] -> x]
{"strings1", "strings2"}