x/evidence/simulation/genesis.go: add unit tests (#6740)

Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>

x/evidence/simulation/genesis_test.go

@@ -0,0 +1,66 @@
+package simulation_test
+
+import (
+	"encoding/json"
+	"math/rand"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+
+	"github.com/cosmos/cosmos-sdk/codec"
+	"github.com/cosmos/cosmos-sdk/types/module"
+	simtypes "github.com/cosmos/cosmos-sdk/types/simulation"
+	"github.com/cosmos/cosmos-sdk/x/evidence/simulation"
+	"github.com/cosmos/cosmos-sdk/x/evidence/types"
+)
+
+// TestRandomizedGenState tests the normal scenario of applying RandomizedGenState.
+// Abonormal scenarios are not tested here.
+func TestRandomizedGenState(t *testing.T) {
+	cdc := codec.New()
+	// Make sure to register cdc.
+	// Otherwise RandomizedGenState will panic!
+	types.RegisterCodec(cdc)
+
+	s := rand.NewSource(1)
+	r := rand.New(s)
+
+	simState := module.SimulationState{
+		AppParams:    make(simtypes.AppParams),
+		Cdc:          cdc,
+		Rand:         r,
+		NumBonded:    3,
+		Accounts:     simtypes.RandomAccounts(r, 3),
+		InitialStake: 1000,
+		GenState:     make(map[string]json.RawMessage),
+	}
+
+	simulation.RandomizedGenState(&simState)
+
+	var evidenceGenesis types.GenesisState
+	simState.Cdc.MustUnmarshalJSON(simState.GenState[types.ModuleName], &evidenceGenesis)
+
+	require.Len(t, evidenceGenesis.Evidence, 0)
+}
+
+// TestRandomizedGenState tests the execution of RandomizedGenState
+// without registering the evidence interfaces.
+// We expect the test to panic.
+func TestRandomizedGenState1(t *testing.T) {
+	cdc := codec.New()
+
+	s := rand.NewSource(1)
+	r := rand.New(s)
+
+	simState := module.SimulationState{
+		AppParams:    make(simtypes.AppParams),
+		Cdc:          cdc,
+		Rand:         r,
+		NumBonded:    3,
+		Accounts:     simtypes.RandomAccounts(r, 3),
+		InitialStake: 1000,
+		GenState:     make(map[string]json.RawMessage),
+	}
+
+	require.Panicsf(t, func() { simulation.RandomizedGenState(&simState) }, "failed to marshal JSON: Unregistered interface exported.Evidence")
+}