Will China conduct a test detonation of a nuclear weapon before 2028?

According to the Arms Control Association's Nuclear Testing Tally, there have been 2,056 nuclear weapons tests around the globe (as of September 6, 2022). This tally includes nuclear weapons testing for military purposes as well as peaceful nuclear explosions, which Wikipedia describes as

. . . nuclear explosions conducted for non-military purposes. Proposed uses include excavation for the building of canals and harbors, electrical generation, the use of nuclear explosions to drive spacecraft, and as a form of wide-area fracking.

The last known nuclear weapons test was conducted by North Korea in September of 2017. However, the US has voiced concerns that China may have conducted nuclear weapons testing recently at their Lop Nur Nuclear Test Base. In particular, a report by the US Department of State from June of 2020 says the following (see page 49):

China’s possible preparation to operate its Lop Nur test site year-round, its use of explosive containment chambers, extensive excavation activities at Lop Nur, and lack of transparency on its nuclear testing activities – which has included frequently blocking the flow of data from its International Monitoring System (IMS) stations to the International Data Center operated by the Preparatory Commission for the Comprehensive Nuclear Test-Ban Treaty Organization – raise concerns regarding its adherence to the “zero yield” standard adhered to by the United States, the United Kingdom, and France in their respective nuclear weapons testing moratoria.

China's last known test was on July 29, 1996 at Lop Nur. On September 24, 1996 China signed the Comprehensive Nuclear-Test-Ban Treaty, but has not ratified it.

Daryl Kimball, Executive Director of the Arms Control Association explained the methodology behind the Arms Control Association's Nuclear Testing Tally in an email as follows:

. . . our [Nuclear Testing Tally fact sheet] takes into account all documented and acknowledged nuclear weapon test explosions and is based on detailed reports published by the U.S. Department of Energy/NNSA, the CTBTO, the Russian atomic energy ministry, and public reports on nuclear test explosions conducted by other countries, which is why we list eight countries that have conducted nuclear test explosions since 1945. In keeping with contemporary interpretations of international law (the NPT and the CTBT), we do not distiguish between so-called peaceful nuclear explosions and nuclear weapon test explosions. Some tallies of nuclear testing vary on the margins, which is often due to whether one counts the number of “nuclear testing” events or “nuclear detonations” (some nuclear test events involved multiple nuclear detonations).

We do pay very close attention to allegations of concealed nuclear weapons testing (concerning Russia and China in particular) and there is of course the debate about whether Israel perhaps, in coordination with South Africa, conducted a nuclear weapon test detonation in 1979 in the outer atmosphere above the South Atlantic. But this simple fact sheet does list or try to describe the debates about some of the allegations about nuclear testing (for instance by Israel or by Russia since it signed and ratified the CTBT).