From that web-page: "The People’s Liberation Army has deployed 2,000 medical personnel to Shanghai with an additional 38,000 medical workers to carry out a mass mitigation effort to test all 26 million city residents for COVID"

Sooo, just to autistically math: 40 000 peeps are to test 26 M locked-up individuals.

Assuming that testees can walk themselves to a testing station:

Each tester is therefore assigned an average of 26000000/40000 = 650 people to test. Many rapid result tests guarantee results in as little as twenty minutes, so that 650 results would take 216.7 working hours to test. Given a gruelling ten-hour working day, this process would take at least three weeks. Of course, these times can overlap, if tests are lined up on a table, and more are tested, while the completed tests go off. But that will create a documentation and tracking issue, which will in turn lengthen the testing time for an entire 26M residents.

The on-site RT-PCR testing is even more problematic, as it creates bottle-necks at the labs. Although they may only take a few hours to process. PCR testing requires lab work that, if backed up by extreme overload, will take many weeks to garner results.

This process becomes even more laborious if testers have to visit individual apartments because of the lockdown rules. Packing materials and notebooks and walking between doors would add time to the overall regime. Furthermore, time-saving such as the previously suggested central 'going-off' table become difficult as such methods may be constrained to one floor of an apartment block, for example.