diff --git a/engine/account_test.go b/engine/account_test.go
index 647876f73..c1c50fe9b 100644
--- a/engine/account_test.go
+++ b/engine/account_test.go
@@ -31,6 +31,7 @@ import (
 
 	"github.com/cgrates/cgrates/config"
 	"github.com/cgrates/cgrates/utils"
+	"github.com/google/go-cmp/cmp"
 )
 
 var (
@@ -3446,3 +3447,102 @@ func TestAccountSummaryString(t *testing.T) {
 		t.Errorf("Error unmarshalling result: %v", err)
 	}
 }
+
+func TestAccountProcessAccountSummaryField(t *testing.T) {
+	type args struct {
+		fldPath    []string
+		accSummary any
+		event      map[string]any
+	}
+	tests := []struct {
+		name    string
+		args    args
+		want    any
+		wantErr bool
+	}{
+		{
+			name: "Direct access for *AccountSummary (Tenant)",
+			args: args{
+				fldPath:    []string{"Tenant"},
+				accSummary: &AccountSummary{Tenant: "test_tenant", ID: "id1"},
+				event:      make(map[string]any),
+			},
+			want:    "test_tenant",
+			wantErr: false,
+		},
+		{
+			name: "Unmarshal with ValueFactors field (expecting error on missing factor)",
+			args: args{
+				fldPath:    []string{"BalanceSummaries", "0", "Factors", "factor1"},
+				accSummary: `{"BalanceSummaries": [{"UUID": "summary1", "Factors": {"factor1": 0.2}}]}`,
+				event:      make(map[string]any),
+			},
+			want:    nil,
+			wantErr: true,
+		},
+		{
+			name: "Error on missing ValueFactors field",
+			args: args{
+				fldPath:    []string{"BalanceSummaries", "0", "Factors", "missing_factor"},
+				accSummary: `{"BalanceSummaries": [{"UUID": "summary1"}]}`,
+				event:      make(map[string]any),
+			},
+			want:    nil,
+			wantErr: true,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got, err := processAccountSummaryField(tt.args.fldPath, tt.args.accSummary, tt.args.event)
+			if (err != nil) != tt.wantErr {
+				t.Errorf("processAccountSummaryField error = %v, wantErr = %v", err, tt.wantErr)
+				return
+			}
+			if diff := cmp.Diff(tt.want, got); diff != "" && !tt.wantErr {
+				t.Errorf("processAccountSummaryField mismatch (-want +got):\n%s", diff)
+			}
+		})
+	}
+}
+
+func TestProcessAccountSummaryFieldNonStringAccSummary(t *testing.T) {
+	type args struct {
+		fldPath    []string
+		accSummary any
+		event      map[string]any
+	}
+
+	tests := []struct {
+		name    string
+		args    args
+		wantErr bool
+	}{
+		{
+			name: "Error on non-string accSummary (marshal)",
+			args: args{
+				fldPath:    []string{"Tenant"},
+				accSummary: map[string]string{"Name": "Test Account"},
+				event:      make(map[string]any),
+			},
+			wantErr: true,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			_, err := processAccountSummaryField(tt.args.fldPath, tt.args.accSummary, tt.args.event)
+			if (err == nil) != tt.wantErr {
+				t.Errorf("processAccountSummaryField error = %v, wantErr = %v", err, tt.wantErr)
+				return
+			}
+		})
+	}
+}
+
+func TestAccountFieldAsInterfaceNilAccount(t *testing.T) {
+	var acc *Account
+	fldPath := []string{"ID"}
+	_, err := acc.FieldAsInterface(fldPath)
+	if err != utils.ErrNotFound {
+		t.Errorf("Expected error %v, got %v", utils.ErrNotFound, err)
+	}
+}
diff --git a/engine/libindex_test.go b/engine/libindex_test.go
index 84e29413b..a6cc12b97 100644
--- a/engine/libindex_test.go
+++ b/engine/libindex_test.go
@@ -81,31 +81,31 @@ func TestLibIndexRemoveFilterIndexesForFilterErrnotFound(t *testing.T) {
 }
 
 func TestLibIndexSplitFilterIndexErrWrongIdxKeyFormat(t *testing.T) {
-	tests := []struct {
-		name         string
-		tntCtxIdxKey string
-		wantErr      string
-	}{
-		{
-			name:         "invalid index key format with less than 4 parts",
-			tntCtxIdxKey: "invalid:key",
-			wantErr:      "WRONG_IDX_KEY_FORMAT<invalid:key>",
-		},
-		{
-			name:         "another invalid index key format with less than 4 parts",
-			tntCtxIdxKey: "another:invalid:key",
-			wantErr:      "WRONG_IDX_KEY_FORMAT<another:invalid:key>",
-		},
-	}
-	for _, tt := range tests {
-		t.Run(tt.name, func(t *testing.T) {
-			_, _, err := splitFilterIndex(tt.tntCtxIdxKey)
-			if err == nil {
-				t.Fatalf("Expected error but got nil")
-			}
-			if err.Error() != tt.wantErr {
-				t.Fatalf("Expected error %v, but got %v", tt.wantErr, err.Error())
-			}
-		})
+	tntCtxIdxKey := "invalid:key"
+	expectedErr := "WRONG_IDX_KEY_FORMAT<invalid:key>"
+	_, _, err := splitFilterIndex(tntCtxIdxKey)
+	if err == nil || err.Error() != expectedErr {
+		t.Fatalf("Expected error %v, got %v", expectedErr, err)
+	}
+}
+
+func TestLibIndexNewFilterIndexGetFilterErrNotFound(t *testing.T) {
+	cfg := config.NewDefaultCGRConfig()
+	dataDB := NewInternalDB(nil, nil, true, cfg.DataDbCfg().Items)
+	dm := NewDataManager(dataDB, cfg.CacheCfg(), nil)
+	tnt := "tenant"
+	ctx := "context"
+	itemID := "item1"
+	filterIDs := []string{"nonexistent_filter"}
+	idxItmType := "indexItemType"
+	newFlt := &Filter{
+		Tenant: tnt,
+		ID:     "filter1",
+		Rules:  []*FilterRule{},
+	}
+	_, err := newFilterIndex(dm, idxItmType, tnt, ctx, itemID, filterIDs, newFlt)
+	expectedErr := "broken reference to filter: nonexistent_filter for itemType: indexItemType and ID: item1"
+	if err == nil || err.Error() != expectedErr {
+		t.Fatalf("Expected error %v, got %v", expectedErr, err)
 	}
 }