In 1953, China fought the US to
support North Korea during the Korea war. After the war, North Korea insisted that it won the war single-handedly. Mao left Kim two divisions of Korean Chinese soldiers because he thought they could help North Korea re-build. Kim was so suspicious of them that he had them quickly murdered.
China was friends with Russia since WWII but during the border conflict in 1969, Russia threatened nuclear attack, which sent the whole northern China into a frenzy of tunnel-digging. Sino-Soviet border conflict
China supported North Vietnam during the US invasion. But as soon as the invasion was over, Vietnam started bombing China and expelling ethnic Chinese Vietnamese (in support of USSR). This eventually led to the Sino-Vietnamese War in 1979.
After 70 years in power, the PRC is getting pretty jaded about this "true friend" thing. The feeling is mutual among most other Asian countries, because during the time when PRC was young and didn't know any better, it bumbled a couple of times with other countries internal affairs that didn't do any lasting good either.
Arms-length relationship based on mutual interest is the way to go.