Update unit tests to support the code modifications related to backwa… #213

Job	Run time
Intra-doc links	3m 45s
Bitrot check	1m 41s
Build target wasm32-unknown-unknown	3m 58s
Book tests	3m 40s
Build target wasm32-wasi	3m 49s
Rustfmt	14s
Test on ubuntu-latest	9m 25s
Test on i686-unknown-linux-gnu	15m 35s
Test on windows-latest	12m 10s
Test on i686-unknown-linux-gnu with beta features	16m 1s
Test on macOS-latest	14m 20s
Test on ubuntu-latest with beta features	9m 24s
Test on i686-unknown-linux-gnu with nightly features	17m 58s
Test on windows-latest with beta features	12m 28s
Test on macOS-latest with beta features	11m 4s
Test on ubuntu-latest with nightly features	10m 32s
Test on windows-latest with nightly features	13m 34s
Test on macOS-latest with nightly features	12m 22s
	2h 52m 0s

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