Use mock server in test #400

Job	Run time
Tests (ubuntu-latest, 7.4, highest, ^5)	1m 30s
Tests (ubuntu-latest, 8.0, highest, ^6)	1m 35s
Tests (ubuntu-latest, 8.1, lowest, ^5)	1m 37s
Tests (ubuntu-latest, 8.0, highest, ^5)	1m 43s
Tests (ubuntu-latest, 8.2, lowest, ^6)	1m 30s
Tests (ubuntu-latest, 8.1, lowest, ^6)	1m 44s
Tests (ubuntu-latest, 8.0, lowest, ^6)	1m 46s
Tests (ubuntu-latest, 8.1, highest, ^5)	1m 37s
Tests (ubuntu-latest, 7.4, lowest, ^5)	1m 27s
Tests (ubuntu-latest, 8.0, lowest, ^5)	1m 39s
Tests (ubuntu-latest, 8.2, highest, ^5)	1m 37s
Tests (ubuntu-latest, 8.1, highest, ^6)	1m 59s
Tests (ubuntu-latest, 8.2, lowest, ^7)	1m 30s
Tests (ubuntu-latest, 8.2, lowest, ^5)	1m 41s
Tests (ubuntu-latest, 8.3, lowest, ^5)	2m 55s
Tests (ubuntu-latest, 8.2, highest, ^6)	1m 40s
Tests (ubuntu-latest, 8.2, highest, ^7)	1m 35s
Tests (ubuntu-latest, 8.3, highest, ^6)	2m 50s
Tests (windows-latest, 8.0, highest, 5.4.2)	40s
Tests (ubuntu-latest, 8.3, lowest, ^7)	2m 41s
Tests (ubuntu-latest, 8.3, highest, ^7)	2m 50s
Tests (ubuntu-latest, 8.3, highest, ^5)	2m 51s
Tests (macos-latest, 8.0, highest, ^5)	3m 26s
Tests (ubuntu-latest, 8.3, lowest, ^6)	2m 42s
	47m 5s

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