Use mock server in test #421

Job	Run time
Tests (ubuntu-latest, 8.3, highest, ^6)	1m 23s
Tests (ubuntu-latest, 7.4, lowest, ^5)	1m 25s
Tests (windows-latest, 8.0, highest, 5.4.2)	2m 47s
Tests (ubuntu-latest, 8.1, highest, ^5)	1m 15s
Tests (ubuntu-latest, 8.0, highest, ^5)	1m 20s
Tests (ubuntu-latest, 8.0, highest, ^6)	1m 26s
Tests (ubuntu-latest, 8.1, highest, ^6)	1m 24s
Tests (ubuntu-latest, 8.1, lowest, ^6)	1m 25s
Tests (ubuntu-latest, 8.3, lowest, ^5)	1m 21s
Tests (ubuntu-latest, 8.2, highest, ^7)	1m 16s
Tests (macos-latest, 8.0, highest, ^5)	2m 7s
Tests (ubuntu-latest, 8.3, lowest, ^6)	1m 34s
Tests (ubuntu-latest, 8.3, lowest, ^7)	1m 30s
Tests (ubuntu-latest, 8.2, lowest, ^7)	1m 29s
Tests (ubuntu-latest, 8.3, highest, ^7)	1m 47s
Tests (ubuntu-latest, 8.2, lowest, ^5)	1m 30s
Tests (ubuntu-latest, 8.0, lowest, ^6)	1m 31s
Tests (ubuntu-latest, 8.2, lowest, ^6)	1m 16s
Tests (ubuntu-latest, 8.0, lowest, ^5)	1m 22s
Tests (ubuntu-latest, 7.4, highest, ^5)	1m 25s
Tests (ubuntu-latest, 8.3, highest, ^5)	1m 19s
Tests (ubuntu-latest, 8.2, highest, ^6)	1m 33s
Tests (ubuntu-latest, 8.1, lowest, ^5)	1m 32s
Tests (ubuntu-latest, 8.2, highest, ^5)	1m 31s
	36m 28s

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