diff --git a/engine/balances_test.go b/engine/balances_test.go
index 8b327c468..f42768636 100644
--- a/engine/balances_test.go
+++ b/engine/balances_test.go
@@ -19,6 +19,7 @@ package engine
 
 import (
 	"bytes"
+	"encoding/json"
 	"log"
 	"os"
 	"strings"
@@ -666,3 +667,113 @@ func TestBalancesValueFactorsGetValue(t *testing.T) {
 		}
 	}
 }
+func TestBalancesStringJson(t *testing.T) {
+	balances := Balances{
+		&Balance{
+			Uuid:           "uuid123",
+			ID:             "balance123",
+			Value:          100.0,
+			ExpirationDate: time.Date(2024, time.December, 31, 23, 59, 59, 0, time.UTC),
+			Weight:         1.5,
+			DestinationIDs: utils.StringMap{},
+			RatingSubject:  "ratingSub",
+			Categories:     utils.StringMap{},
+			SharedGroups:   utils.StringMap{},
+			Timings:        []*RITiming{},
+			TimingIDs:      utils.StringMap{},
+			Disabled:       false,
+			Blocker:        true,
+			precision:      2,
+			account:        nil,
+			dirty:          false,
+		},
+	}
+
+	result := balances.String()
+	if result == "" {
+		t.Error("Expected non-empty JSON string, but got empty string")
+	}
+}
+
+func TestBalanceFieldAsString(t *testing.T) {
+	balance := &Balance{
+		Uuid: "uuid123",
+	}
+	val, err := balance.FieldAsString([]string{"Uuid"})
+	if err != nil {
+		t.Errorf("Unexpected error for field 'Uuid': %v", err)
+	}
+	expected := balance.Uuid
+	if val != expected {
+		t.Errorf("Expected value '%s' for field 'Uuid', but got '%s'", expected, val)
+	}
+	_, err = balance.FieldAsString([]string{"InvalidField"})
+	if err == nil {
+		t.Error("Expected error for invalid field path, but got nil")
+	}
+}
+
+func TestBalancesString(t *testing.T) {
+	balance := &Balance{
+		Uuid: "123e4567-e89b-12d3-a456-426614174000",
+	}
+	jsonStr := balance.String()
+	var data map[string]interface{}
+	err := json.Unmarshal([]byte(jsonStr), &data)
+	if err != nil {
+		t.Errorf("Error unmarshalling JSON string: %v", err)
+	}
+	expectedUuid := balance.Uuid
+	if uuid, ok := data["Uuid"].(string); !ok || uuid != expectedUuid {
+		t.Errorf("Expected Uuid '%s' in JSON, but got '%v'", expectedUuid, data["Uuid"])
+	}
+}
+func TestBalancesHasBalanceReturn(t *testing.T) {
+	balances := Balances{
+		{ID: "1"},
+		{ID: "2"},
+		{ID: "3"},
+	}
+	existingBalance := &Balance{ID: "2"}
+	if !balances.HasBalance(existingBalance) {
+		t.Errorf("Expected balance with ID '%s' to exist, but it does not", existingBalance.ID)
+	}
+	nonExistingBalance := &Balance{ID: "4"}
+	if balances.HasBalance(nonExistingBalance) {
+		t.Errorf("Expected balance with ID '%s' to not exist, but it does", nonExistingBalance.ID)
+	}
+}
+
+func TestBalancesEqual(t *testing.T) {
+	balances1 := Balances{
+		{ID: "1"},
+		{ID: "2"},
+		{ID: "3"},
+	}
+	balances2 := Balances{
+		{ID: "1"},
+		{ID: "2"},
+		{ID: "3"},
+	}
+	if !balances1.Equal(balances1) {
+		t.Errorf("Expected balances1 to equal itself, but it does not")
+	}
+	if !balances1.Equal(balances2) {
+		t.Errorf("Expected balances1 to equal balances2, but they are not equal")
+	}
+	balances3 := Balances{
+		{ID: "1"},
+		{ID: "2"},
+	}
+	if balances1.Equal(balances3) {
+		t.Errorf("Expected balances1 to not equal balances3, but they are equal")
+	}
+	balances4 := Balances{
+		{ID: "1"},
+		{ID: "2"},
+		{ID: "4"},
+	}
+	if balances1.Equal(balances4) {
+		t.Errorf("Expected balances1 to not equal balances4, but they are equal")
+	}
+}
diff --git a/engine/eventcost_test.go b/engine/eventcost_test.go
index 8d9bb7bae..8388d1849 100644
--- a/engine/eventcost_test.go
+++ b/engine/eventcost_test.go
@@ -18,12 +18,14 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>
 package engine
 
 import (
+	"errors"
 	"fmt"
 	"reflect"
 	"testing"
 	"time"
 
 	"github.com/cgrates/cgrates/config"
+
 	"github.com/cgrates/cgrates/utils"
 )
 
@@ -4842,3 +4844,135 @@ func TestECfieldAsInterfaceNilECCost(t *testing.T) {
 		t.Errorf("\nexpected: <%+v>, \nreceived: <%+v>", nil, rcv)
 	}
 }
+
+func TestEventCostSet(t *testing.T) {
+	ec := &EventCost{}
+	testCases := []struct {
+		name    string
+		fldPath []string
+		val     interface{}
+		wantErr error
+	}{
+		{
+			name:    "cgrates",
+			fldPath: []string{"field1"},
+			val:     "value1",
+			wantErr: utils.ErrNotImplemented,
+		},
+		{
+			name:    "cgrates2",
+			fldPath: []string{"field2", "subfield"},
+			val:     123,
+			wantErr: utils.ErrNotImplemented,
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+
+			err := ec.Set(tc.fldPath, tc.val)
+
+			if err != tc.wantErr {
+				t.Errorf("Set() error = %v, wantErr %v", err, tc.wantErr)
+			}
+		})
+	}
+}
+
+func TestEventCostRemove(t *testing.T) {
+	ec := &EventCost{}
+	testCases := []struct {
+		name    string
+		fldPath []string
+		wantErr error
+	}{
+		{
+			name:    "cgrates",
+			fldPath: []string{"field1"},
+			wantErr: utils.ErrNotImplemented,
+		},
+		{
+			name:    "cgrates2",
+			fldPath: []string{"field2", "subfield"},
+			wantErr: utils.ErrNotImplemented,
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+
+			err := ec.Remove(tc.fldPath)
+
+			if err != tc.wantErr {
+				t.Errorf("Remove() error = %v, wantErr %v", err, tc.wantErr)
+			}
+		})
+	}
+}
+
+func TestEventCostGetKeys(t *testing.T) {
+	ec := &EventCost{}
+	testCases := []struct {
+		name         string
+		nested       bool
+		nestedLimit  int
+		prefix       string
+		expectedKeys []string
+	}{
+		{
+			name:         "cgrates",
+			nested:       true,
+			nestedLimit:  3,
+			prefix:       "prefix",
+			expectedKeys: nil,
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+
+			keys := ec.GetKeys(tc.nested, tc.nestedLimit, tc.prefix)
+
+			if !reflect.DeepEqual(keys, tc.expectedKeys) {
+				t.Errorf("GetKeys() returned %+v, expected %+v", keys, tc.expectedKeys)
+			}
+		})
+	}
+}
+
+func TestEvenCostProcessEventCostField(t *testing.T) {
+
+	testCases := []struct {
+		name          string
+		fldPath       []string
+		cd            interface{}
+		event         map[string]interface{}
+		expectedValue interface{}
+		expectedErr   error
+	}{
+		{
+			name:          "cgrates",
+			fldPath:       []string{"field1"},
+			cd:            nil,
+			event:         make(map[string]interface{}),
+			expectedValue: nil,
+			expectedErr:   errors.New("unsupported field prefix: <field1>"),
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+
+			val, err := processEventCostField(tc.fldPath, tc.cd, tc.event)
+
+			if !reflect.DeepEqual(val, tc.expectedValue) {
+				t.Errorf("ProcessEventCostField() returned %+v, expected %+v", val, tc.expectedValue)
+			}
+
+			if (err == nil && tc.expectedErr != nil) || (err != nil && tc.expectedErr == nil) || (err != nil && tc.expectedErr != nil && err.Error() != tc.expectedErr.Error()) {
+				t.Errorf("ProcessEventCostField() error = %v, expected error = %v", err, tc.expectedErr)
+			}
+
+		})
+	}
+}
diff --git a/engine/exportrequest_test.go b/engine/exportrequest_test.go
index 701360a4e..f74f01bc6 100644
--- a/engine/exportrequest_test.go
+++ b/engine/exportrequest_test.go
@@ -667,3 +667,11 @@ func TestExportRequestSetFields2(t *testing.T) {
 		t.Error(err)
 	}
 }
+
+func TestExportRequestString(t *testing.T) {
+	eeR := &ExportRequest{}
+	jsonStr := eeR.String()
+	if jsonStr == "" {
+		t.Errorf("Expected non-empty JSON string, but got empty")
+	}
+}
diff --git a/engine/globalvars_test.go b/engine/globalvars_test.go
index 29682726b..2ebdf9d11 100644
--- a/engine/globalvars_test.go
+++ b/engine/globalvars_test.go
@@ -18,6 +18,7 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>
 package engine
 
 import (
+	"net/http"
 	"testing"
 )
 
@@ -47,3 +48,11 @@ func TestSetDataStorage(t *testing.T) {
 	}
 	dm = tmp
 }
+
+func TestGlobalvarsGetHTTPPstrTransport(t *testing.T) {
+	httpPstrTransport = &http.Transport{}
+	transport := GetHTTPPstrTransport()
+	if transport == nil {
+		t.Error("Expected transport to be initialized, but got nil")
+	}
+}
diff --git a/engine/libchargers_test.go b/engine/libchargers_test.go
new file mode 100644
index 000000000..256363750
--- /dev/null
+++ b/engine/libchargers_test.go
@@ -0,0 +1,110 @@
+/*
+Real-time Online/Offline Charging System (OCS) for Telecom & ISP environments
+Copyright (C) ITsysCOM GmbH
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <http://www.gnu.org/licenses/>
+*/
+
+package engine
+
+import (
+	"testing"
+)
+
+func TestLibChargersSort(t *testing.T) {
+	tests := []struct {
+		name   string
+		input  ChargerProfiles
+		output ChargerProfiles
+	}{
+		{
+			"AlreadySorted",
+			ChargerProfiles{
+				{Weight: 5},
+				{Weight: 3},
+				{Weight: 1},
+			},
+			ChargerProfiles{
+				{Weight: 5},
+				{Weight: 3},
+				{Weight: 1},
+			},
+		},
+		{
+			"Unsorted",
+			ChargerProfiles{
+				{Weight: 1},
+				{Weight: 5},
+				{Weight: 3},
+			},
+			ChargerProfiles{
+				{Weight: 5},
+				{Weight: 3},
+				{Weight: 1},
+			},
+		},
+		{
+			"AllSameWeight",
+			ChargerProfiles{
+				{Weight: 2},
+				{Weight: 2},
+				{Weight: 2},
+			},
+			ChargerProfiles{
+				{Weight: 2},
+				{Weight: 2},
+				{Weight: 2},
+			},
+		},
+		{
+			"SingleElement",
+			ChargerProfiles{
+				{Weight: 4},
+			},
+			ChargerProfiles{
+				{Weight: 4},
+			},
+		},
+		{
+			"Empty",
+			ChargerProfiles{},
+			ChargerProfiles{},
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			tt.input.Sort()
+			if len(tt.input) != len(tt.output) {
+				t.Errorf("expected length %d, got %d", len(tt.output), len(tt.input))
+			}
+			for i := range tt.input {
+				if tt.input[i].Weight != tt.output[i].Weight {
+					t.Errorf("at index %d, expected Weight %f, got %f", i, tt.output[i].Weight, tt.input[i].Weight)
+				}
+			}
+		})
+	}
+}
+
+func TestLibChargersTenantID(t *testing.T) {
+	cp := &ChargerProfile{
+		Tenant: "cgrates.org",
+		ID:     "2012",
+	}
+	result := cp.TenantID()
+	expected := "cgrates.org:2012"
+	if result != expected {
+		t.Errorf("TenantID() = %v, want %v", result, expected)
+	}
+}