China’s six-month-old campaign to calm share markets will be put to the test when stocks reopen on Tuesday, a day after selling triggered an unprecedented trading halt and risked undermining state rescue efforts estimated to have cost around $140 billion. China’s major stock exchanges tanked on the first trading day of the year on Monday, triggering a “circuit-breaker” that halted equities trade nationwide for the first time and put at risk months of regulatory work to restore market stability.