unit tests for saving data #6856

Job	Run time
test-utils-js	17s
test-utils-py	13s
setup	1s
base-build-mac	12m 12s
base-build-windows	8m 52s
bb-on-different-os (windows-latest)	23m 51s
debug	0s
bb-on-different-os (macos-latest)	59m 15s
full-build-base	3h 10m 42s
full-build-LTS	2h 39m 39s
installer-for-osx	2m 26s
installer-for-windows	2m 33s
installer-for-debian	2m 6s
	7h 42m 7s

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