evm: fixed commented out simulations, pubsub, and handler tests (#655)

* evm: fixed commented out simulations, pubsub, and handler tests

fixes #640

simulations are very basic: they can be built and executed,
but they don't generate any EVM-related transactions yet.
(It should be a matter of adding simulation-related code to the
modules + potentially extra helpers to the simulation.)
handler tests miss some extra assertions due to changes
in the return values snapshotting logic (ADR-001 and ADR-002).

Besides the test suites identified in the audit,
there's also "importer_test.go" which wasn't yet fixed.
(it'd require major rewriting + extra test resources)

* gofumpt

x/feemarket/module.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"encoding/json"
 	"fmt"
+	"math/rand"
 
 	"github.com/gorilla/mux"
 	"github.com/grpc-ecosystem/grpc-gateway/runtime"
@@ -16,9 +17,11 @@ import (
 	codectypes "github.com/cosmos/cosmos-sdk/codec/types"
 	sdk "github.com/cosmos/cosmos-sdk/types"
 	"github.com/cosmos/cosmos-sdk/types/module"
+	simtypes "github.com/cosmos/cosmos-sdk/types/simulation"
 
 	"github.com/tharsis/ethermint/x/feemarket/client/cli"
 	"github.com/tharsis/ethermint/x/feemarket/keeper"
+	"github.com/tharsis/ethermint/x/feemarket/simulation"
 	"github.com/tharsis/ethermint/x/feemarket/types"
 )
 
@@ -155,3 +158,26 @@ func (am AppModule) ExportGenesis(ctx sdk.Context, cdc codec.JSONCodec) json.Raw
 	gs := ExportGenesis(ctx, am.keeper)
 	return cdc.MustMarshalJSON(gs)
 }
+
+// RandomizedParams creates randomized fee market param changes for the simulator.
+func (AppModule) RandomizedParams(r *rand.Rand) []simtypes.ParamChange {
+	return nil
+}
+
+// RegisterStoreDecoder registers a decoder for fee market module's types
+func (am AppModule) RegisterStoreDecoder(sdr sdk.StoreDecoderRegistry) {}
+
+// ProposalContents doesn't return any content functions for governance proposals.
+func (AppModule) ProposalContents(simState module.SimulationState) []simtypes.WeightedProposalContent {
+	return nil
+}
+
+// GenerateGenesisState creates a randomized GenState of the fee market module.
+func (AppModule) GenerateGenesisState(simState *module.SimulationState) {
+	simulation.RandomizedGenState(simState)
+}
+
+// WeightedOperations returns the all the fee market module operations with their respective weights.
+func (am AppModule) WeightedOperations(simState module.SimulationState) []simtypes.WeightedOperation {
+	return nil
+}