tests

Use `Replica::pending_tasks` #427

Job	Run time
coverage	3m 16s
tests (Fedora 40, ubuntu-latest, fedora40)	3m 53s
tests (Mac OS 13.latest)	0s
tests (Mac OS 12.latest)	0s
tests (Fedora 39, ubuntu-latest, fedora39)	4m 12s
tests (Debian Testing, ubuntu-latest, debiantesting)	3m 49s
tests (Ubuntu 20.04, ubuntu-latest, ubuntu2004)	4m 21s
tests (Ubuntu 22.04, ubuntu-latest, ubuntu2204)	3m 55s
tests (OpenSUSE Tumbleweed (Rolling), ubuntu-latest, opensuse)	4m 15s
tests (Archlinux Base (Rolling), ubuntu-latest, arch)	4m 5s
	31m 46s

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