x/mint/simulation/params.go: add unit tests (#6708)

Co-authored-by: Federico Kunze <31522760+fedekunze@users.noreply.github.com>
Co-authored-by: Alessio Treglia <alessio@tendermint.com>

x/mint/simulation/params_test.go

@@ -0,0 +1,38 @@
+package simulation_test
+
+import (
+	"math/rand"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+
+	"github.com/cosmos/cosmos-sdk/x/mint/simulation"
+)
+
+func TestParamChangest(t *testing.T) {
+	s := rand.NewSource(1)
+	r := rand.New(s)
+
+	expected := []struct {
+		composedKey string
+		key         string
+		simValue    string
+		subspace    string
+	}{
+		{"mint/InflationRateChange", "InflationRateChange", "\"0.230000000000000000\"", "mint"},
+		{"mint/InflationMax", "InflationMax", "\"0.200000000000000000\"", "mint"},
+		{"mint/InflationMin", "InflationMin", "\"0.070000000000000000\"", "mint"},
+		{"mint/GoalBonded", "GoalBonded", "\"0.670000000000000000\"", "mint"},
+	}
+
+	paramChanges := simulation.ParamChanges(r)
+	require.Len(t, paramChanges, 4)
+
+	for i, p := range paramChanges {
+		require.Equal(t, expected[i].composedKey, p.ComposedKey())
+		require.Equal(t, expected[i].key, p.Key())
+		require.Equal(t, expected[i].simValue, p.SimValue()(r))
+		require.Equal(t, expected[i].subspace, p.Subspace())
+	}
+
+}