Unexpected behaviour of fixture loaders

[pdyraga]

To replicate the problem, please check out b698022 and run yarn test.

The fix was applied in 9738385 but the root cause is still unknown.

Let's say there is a unit test calling await waffle.loadFixture(bridgeFixture) in the setup. For example, Bridge.Wallets.test.ts.

Then, VendingMachine.test.ts loads await waffle.loadFixture(vendingMachineFixture) and modifies the state of VendingMachine by transferVendingMachineUpgradeInitiatorRole to some address.

Finally, some other test starts and that test calls await waffle.loadFixture(bridgeFixture). For example, TBTCVault.Redemption.test.ts. THIS TEST WILL OBSERVE CHANGES DONE BY VendingMachine.test.ts. For example, the upgrade initiator will be the address set by VendingMachine.test.ts.

This is not happening if we use await waffle.loadFixture(bridgeFixture) in all three tests. The root cause is unkown, we suspect it is some clash between plugins.