[WIP]: Adding foundry fuzzer for libraries processing bitmaps

[LHerskind]

Work in progress to add foundry fuzz test of libraries that perform low-level operations on bitmaps etc. Needs #632.

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[m1guelpf]

Suggested change

	"setup:foundry": "foundryup && git submodule update --init",
	"setup:foundry": "foundryup && forge install",

[mds1]

assume should mainly be used for very narrow checks—broad checks will slow down tests as it will take a while to find valid values, and the test may fail if you hit the max number of rejects. (You can also configure fuzz-max-local-rejects and fuzz-max-global-rejects in the foundry.toml file).

I'd recommend changing this test (and similar for other assume usage in the repo) to either:

  function testDecodeSupplyWithPermitParams(
    uint8 assetId, // changed from uint16 to uint8 to reduce number of rejects
    uint128 amount,
    uint16 referralCode,
    uint32 deadLine, // changed to uint32 so fuzzer max value for this param is now type(uint32).max
    uint8 permitV
  ) public {
    VM.assume(assetId < 128);

OR, when solidity's types aren't a great fit, use a uint256 and wrap values manually with modulo, either using Solmate's bound method or just using modulo directly (you want uint256 to reduce modulo bias). A downside of this approach is that when a test fails, you need to take the mod of the failed input to see the actual value used in tests

  function testDecodeSupplyWithPermitParams(
    uint256 assetId, // changed to uint256
    uint128 amount,
    uint16 referralCode,
    uint256 deadLine, // changed to uint256
    uint8 permitV
  ) public {
    assetId = assetId % 128; // wrap assetId between 0 and 127
    deadLine = deadLine % 2**32; // wraps deadLine between 0 and 2**32 - 1
    // or use `bound(val, min, max)` to wrap between min and max, inclusive

[mds1]

DSTest has HEVM_ADDRESS as a constant so you can use that directly for readability. You can also declared this VM variable just once in TestHelper instead of in each individual test contract 🙂

Suggested change

	Vm constant VM = Vm(0x7109709ECfa91a80626fF3989D68f67F5b1DD12D);
	Vm constant VM = Vm(HEVM_ADDRESS);

[LHerskind]

Closing this one since a more updated version in in #967 and I do no longer have credentials to push on top of this one 🫡