Add tests for wrap store loader.

app/.db/CURRENT

@@ -0,0 +1 @@
+MANIFEST-000000

app/.db/LOG

@@ -0,0 +1,6 @@
+=============== Jan 5, 2024 (EST) ===============
+10:42:43.970756 log@legend F·NumFile S·FileSize N·Entry C·BadEntry B·BadBlock Ke·KeyError D·DroppedEntry L·Level Q·SeqNum T·TimeElapsed
+10:42:44.004968 db@open opening
+10:42:44.005399 version@stat F·[] S·0B[] Sc·[]
+10:42:44.010304 db@janitor F·2 G·0
+10:42:44.010345 db@open done T·5.349541ms

app/store_loader.go

@@ -1,6 +1,7 @@
 package app
 
 import (
+	"errors"
 	"fmt"
 	"strconv"
 	"time"
@@ -13,12 +14,19 @@ import (
 	dbm "github.com/tendermint/tm-db"
 )
 
+type StoreLoaderWrapper func(sdk.CommitMultiStore, baseapp.StoreLoader) error
+
 // WrapStoreLoader creates a new StoreLoader by wrapping an existing one.
-func WrapStoreLoader(wrapper func(sdk.CommitMultiStore, baseapp.StoreLoader) error, storeLoader baseapp.StoreLoader) baseapp.StoreLoader {
+func WrapStoreLoader(wrapper StoreLoaderWrapper, storeLoader baseapp.StoreLoader) baseapp.StoreLoader {
 	return func(ms sdk.CommitMultiStore) error {
 		if storeLoader == nil {
 			storeLoader = baseapp.DefaultStoreLoader
 		}
+
+		if wrapper == nil {
+			return errors.New("wrapper must not be nil")
+		}
+
 		return wrapper(ms, storeLoader)
 	}
 }

app/store_loader_test.go

@@ -1,11 +1,82 @@
 package app
 
-import "testing"
+import (
+	"testing"
+
+	"github.com/cosmos/cosmos-sdk/baseapp"
+	"github.com/cosmos/cosmos-sdk/store/rootmulti"
+	sdk "github.com/cosmos/cosmos-sdk/types"
+	"github.com/stretchr/testify/assert"
+	dbm "github.com/tendermint/tm-db"
+)
 
 func TestWrapStoreLoader(t *testing.T) {
+	var flag bool
+	tests := []struct {
+		name        string
+		storeLoader baseapp.StoreLoader
+		wrapper     StoreLoaderWrapper
+		err         string
+	}{
+		{
+			name:        "nil store loader is set with valid value",
+			storeLoader: nil,
+			wrapper:     createMockStoreWrapper(&flag),
+		},
+		{
+			name:        "nil wrapper is handled",
+			storeLoader: createMockStoreLoader(),
+			wrapper:     nil,
+			err:         "wrapper must not be nil",
+		},
+		{
+			name:        "contents of wrapper are called",
+			storeLoader: createMockStoreLoader(),
+			wrapper:     createMockFlipWrapper(&flag),
+		},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			storeLoader := WrapStoreLoader(tc.wrapper, tc.storeLoader)
+			db := dbm.GoLevelDB{}
+			ms := rootmulti.NewStore(&db, nil)
+			assert.NotNil(t, ms, "should create a new multistore for testing")
+			flag = false
+
+			err := storeLoader(ms)
+			if len(tc.err) > 0 {
+				assert.EqualError(t, err, tc.err, "should have correct error")
+				assert.False(t, flag, "wrapper should not be executed")
+			} else {
+				assert.NoError(t, err, "should not return an error on success")
+				assert.True(t, flag, "wrapper should execute and have correct logic")
+			}
 
+		})
+	}
 }
 
 func TestPruningWrapper(t *testing.T) {
 
 }
+
+func createMockStoreLoader() baseapp.StoreLoader {
+	return func(ms sdk.CommitMultiStore) error {
+		return nil
+	}
+}
+
+func createMockFlipWrapper(flag *bool) StoreLoaderWrapper {
+	return func(cms sdk.CommitMultiStore, sl baseapp.StoreLoader) error {
+		*flag = !(*flag)
+		return nil
+	}
+}
+
+func createMockStoreWrapper(flag *bool) StoreLoaderWrapper {
+	return func(cms sdk.CommitMultiStore, sl baseapp.StoreLoader) error {
+		*flag = sl != nil
+		return nil
+	}
+}