refactor: Add Tips decorator in simapp (#12016)

## Description

ref: #11985 (comment)



---

### Author Checklist

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please add links to any relevant follow up issues.*

I have...

- [ ] included the correct [type prefix](https://github.com/commitizen/conventional-commit-types/blob/v3.0.0/index.json) in the PR title
- [ ] added `!` to the type prefix if API or client breaking change
- [ ] targeted the correct branch (see [PR Targeting](https://github.com/cosmos/cosmos-sdk/blob/main/CONTRIBUTING.md#pr-targeting))
- [ ] provided a link to the relevant issue or specification
- [ ] followed the guidelines for [building modules](https://github.com/cosmos/cosmos-sdk/blob/main/docs/building-modules)
- [ ] included the necessary unit and integration [tests](https://github.com/cosmos/cosmos-sdk/blob/main/CONTRIBUTING.md#testing)
- [ ] added a changelog entry to `CHANGELOG.md`
- [ ] included comments for [documenting Go code](https://blog.golang.org/godoc)
- [ ] updated the relevant documentation or specification
- [ ] reviewed "Files changed" and left comments if necessary
- [ ] confirmed all CI checks have passed

### Reviewers Checklist

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your handle next to the items reviewed if you only reviewed selected items.*

I have...

- [ ] confirmed the correct [type prefix](https://github.com/commitizen/conventional-commit-types/blob/v3.0.0/index.json) in the PR title
- [ ] confirmed `!` in the type prefix if API or client breaking change
- [ ] confirmed all author checklist items have been addressed 
- [ ] reviewed state machine logic
- [ ] reviewed API design and naming
- [ ] reviewed documentation is accurate
- [ ] reviewed tests and test coverage
- [ ] manually tested (if applicable)

simapp/app.go

@@ -454,17 +454,15 @@ func NewSimApp(
 	//
 	// The SDK exposes a default postHandlers chain, which comprises of only
 	// one decorator: the Transaction Tips decorator. However, some chains do
-	// not need it by default, so the following line is commented out. You can
-	// uncomment it to include the tips decorator, or define your own
-	// postHandler chain. To read more about tips:
+	// not need it by default, so feel free to comment the next line if you do
+	// not need tips.
+	// To read more about tips:
 	// https://docs.cosmos.network/main/core/tips.html
 	//
 	// Please note that changing any of the anteHandler or postHandler chain is
 	// likely to be a state-machine breaking change, which needs a coordinated
 	// upgrade.
-	//
-	// Uncomment to enable postHandlers:
-	// app.setPostHandler()
+	app.setPostHandler()
 
 	if loadLatest {
 		if err := app.LoadLatestVersion(); err != nil {

x/auth/client/testutil/suite.go

@@ -1562,13 +1562,6 @@ func (s *IntegrationTestSuite) TestAuxSigner() {
 }
 
 func (s *IntegrationTestSuite) TestAuxToFeeWithTips() {
-	// Currently, simapp doesn't have Tips decorator enabled by default in its
-	// posthandlers, so this test will fail.
-	//
-	// TODO Find a way to test Tips integratin test with a custom simapp with
-	// tips posthandler.
-	s.T().Skip()
-
 	require := s.Require()
 	val := s.network.Validators[0]
 

x/auth/tx/service_test.go

@@ -145,8 +145,14 @@ func (s IntegrationTestSuite) TestSimulateTx_GRPC() {
 			} else {
 				s.Require().NoError(err)
 				// Check the result and gas used are correct.
-				s.Require().Equal(len(res.GetResult().GetEvents()), 6) // 1 coin recv 1 coin spent, 1 transfer, 3 messages.
-				s.Require().True(res.GetGasInfo().GetGasUsed() > 0)    // Gas used sometimes change, just check it's not empty.
+				//
+				// The 13 events are:
+				// - Sending Fee to the pool: coin_spent, coin_received, transfer and message.sender=<val1>
+				// - tx.* events: tx.fee, tx.acc_seq, tx.signature
+				// - Sending Amount to recipient: coin_spent, coin_received, transfer and message.sender=<val1>
+				// - Msg events: message.module=bank and message.action=/cosmos.bank.v1beta1.MsgSend
+				s.Require().Equal(len(res.GetResult().GetEvents()), 13) // 1 coin recv 1 coin spent, 1 transfer, 3 messages.
+				s.Require().True(res.GetGasInfo().GetGasUsed() > 0)     // Gas used sometimes change, just check it's not empty.
 			}
 		})
 	}
@@ -187,8 +193,8 @@ func (s IntegrationTestSuite) TestSimulateTx_GRPCGateway() {
 				s.Require().NoError(err)
 				// Check the result and gas used are correct.
 				s.Require().Len(result.GetResult().MsgResponses, 1)
-				s.Require().Equal(len(result.GetResult().GetEvents()), 6) // 1 coin recv 1 coin spent, 1 transfer, 3 messages.
-				s.Require().True(result.GetGasInfo().GetGasUsed() > 0)    // Gas used sometimes change, jus
+				s.Require().Equal(len(result.GetResult().GetEvents()), 13) // See TestSimulateTx_GRPC for the 13 events.
+				s.Require().True(result.GetGasInfo().GetGasUsed() > 0)     // Gas used sometimes change, jus
 			}
 		})
 	}