cosmos sdk provides a powerful simulation testing capability, and one of the simulation modes TestFullAppSimulation allows for simulation testing using data from genesis.json. The original implementation can be found at #3428. However, with the release of v0.40.0, there have been significant changes to the code and TestFullAppSimulation is no longer being maintained.

The following are my steps:

To begin, the chain-related data can be initialized using the following command, at least 2 accounts must be added for genesis account, otherwise when executing SimulateMsgSend, two accounts will be selected to meet the conditions from != to and it will fall into an infinite loop.

simd init cosmos --chain-id simulation-app

simd keys add my_validator --keyring-backend test

MY_VALIDATOR_ADDRESS=$(simd keys show my_validator -a --keyring-backend test)

simd genesis add-genesis-account $MY_VALIDATOR_ADDRESS 100000000000stake
simd genesis add-genesis-account cosmos1gfg9ucc7rrzc207y9qfmf58erftzf8z8ww5lr7 100000000000stake
simd genesis add-genesis-account cosmos1lh6pmahlkytz7lmrs25a42j6kxlmztyt204kyq 100000000000stake
simd genesis add-genesis-account cosmos18v3mjs2pmssd03v0qz80fr0u2j5p7lxw8nchxg 100000000000stake

simd genesis gentx my_validator 100000000stake --chain-id simulation-app --keyring-backend test

simd genesis collect-gentxs

Then, in the latest main branch, execute the command make test-sim-custom-genesis-fast (note: you need to modify -Genesis=${HOME}/.gaiad/config/genesis.json to -Genesis=${HOME}/.simapp/config/genesis.json in the Makefile first). You may encounter the following error:

Running custom genesis simulation...
By default, /Users/lcq/.gaiad/config/genesis.json will be used.
=== RUN   TestFullAppSimulation
Starting SimulateFromSeed with randomness created with seed 99
Randomized simulation params: 
{}
Selected randomly generated consensus parameters:
{
 "block": {
  "max_bytes": 21456269,
  "max_gas": -1
 },
 "evidence": {
  "max_age_num_blocks": 302400,
  "max_age_duration": 1814400000000000
 },
 "validator": {
  "pub_key_types": [
   "ed25519"
  ]
 }
}
Starting the simulation from time Wed Sep 27 15:49:06 UTC 2023 (unixtime 1695829746)
Simulating... block 1/100, operation 0/269. Logs to writing to /Users/lcq/.simapp/simulations/2023-09-28_00:18:10.log
    simulate.go:347: error on block  1/100, operation (1/269) from x/group:
        group: not found [cosmos/cosmos-sdk/x/group/keeper/grpc_query.go:27]
        Comment: 
--- FAIL: TestFullAppSimulation (0.12s)
FAIL

Based on the errors encountered during each execution of make test-sim-custom-genesis-fast, I have identified and attempted to resolve three potential issues:

Issue 1: Fix the problem where the account randomly generated by AppStateFromGenesisFileFn does not have a ConsKey, causing SimulateMsgCreateValidator to fail.
This issue primarily arises when executing SimulateMsgCreateValidator. The accounts generated by AppStateFromGenesisFileFn do not have the ConsKey field specified, leading to a null pointer exception when calling simAccount.ConsKey.PubKey().

Issue 2: Fix the problem of operating on a group, such as SimulateMsgCreateGroupPolicy, when the group does not exist in the chain during simulation testing.
The problem is encountered when executing the simulation test of the group module. It occurs when there is no group created, meaning there is no group in the chain. Some operations are performed on an empty group, such as executing SimulateMsgCreateGroupPolicy.

Issue 3: Add the SigverifyTx flag in the simulation test whether to check the transaction signature.
During the execution of AppStateFromGenesisFileFn, the private keys corresponding to addresses are generated randomly. Therefore, when executing transactions, we need to skip the signature verification check.
Of course, if the genesis data is also randomly generated, such as the simulation test executed by the make test-sim-nondeterminism command, the private key corresponding to the address generated at this time is correct, and the signature needs to be verified at this time.
Or when we also read the data initialization chain from the genesis.json file. If the private keys corresponding to all addresses are passed in, we can also verify the signature at this time.
So I added a SigverifyTx flag that leaves it up to the user to decide whether signature verification of the transaction is required. For example, if I want to skip signature verification when executing simulation, then I can run go test -mod=readonly -run TestFullAppSimulation -Genesis=genesis.json -SigverifyTx=false