Testing multiple HTTP callouts. System.CalloutException: You have uncommitted work pending. Please commit or rollback before calling out.

Here is the Controller:

global class BoxAccountFolderWidgetController {
    global string WidgetLink {set;
                              get
                              {
                                  return WLink;
                              }
                             }
    public string AccntId = ApexPages.currentPage().getParameters().get('id'); 
    public Account ac = [select id, name, RecordTypeId, Box_Folder_ID__c from Account where id=:AccntId];
    public string BoxFolderId = ac.Box_Folder_ID__c;
    public BoxRefreshToken__c BoxCS = [select id, RefreshToken__c, ClientId__c, ClientSecret__c from BoxRefreshToken__c limit 1];
    public string ClientId = BoxCS.ClientId__c;
    public string ClientSecret = BoxCS.ClientSecret__c;
    public string RefreshToken = BoxCS.RefreshToken__c;
    public string endPointURL='';
    public string AccessToken='';
    public string SharedLink='';
    public string WLink='';
    String Response ='';
    global BoxAccountFolderWidgetController(ApexPages.StandardController controller) 
    {
    }
    global void WidgetMethod()
    {
        system.debug('RefreshToken '+RefreshToken);
        //Getting Access Token and Refresh Token
        HttpRequest req = new HttpRequest();
        endpointURL = 'https://api.box.com/oauth2/token';
        req.setEndpoint(endPointURL);
        req.setMethod('POST');
        req.setHeader('Content-Type','application/x-www-form-urlencoded');
        req.setbody('grant_type=refresh_token'+
                    '&refresh_token='+RefreshToken+
                    '&client_id='+ClientId+
                    '&client_secret='+ClientSecret);
        req.setHeader('Accept','application/json');
        Http http = new Http();
        HTTPResponse res = http.send(req);
        Response=res.getBody();
        system.debug('Response '+Response);
        Integer statusCode=res.getStatusCode();
        // Parse JSON response to get AccessToken and RefreshToken values.
        JSONParser parser = JSON.createParser(Response);
        while(parser.nextToken() != null) 
        {
            if((parser.getCurrentToken() == JSONToken.FIELD_NAME))
            {
                String fieldName = parser.getText();
                parser.nextToken();
                if(fieldName == 'access_token') {
                    AccessToken = parser.getText();
                }
                if(fieldName == 'refresh_token') 
                {
                    RefreshToken = parser.getText();
                }
            }
        }
        system.debug('AccessToken '+AccessToken);
        system.debug('RefreshToken '+RefreshToken);
        //Creating Shared Link for the Folder
        HttpRequest req2 = new HttpRequest();
        endpointURL = 'https://api.box.com/2.0/folders/'+BoxFolderId;
        req2.setEndpoint(endpointURL);
        req2.setMethod('PUT');
        req2.setHeader('Content-Type','application/x-www-form-urlencoded');
        req2.setHeader('Accept','application/json');
        req2.setHeader('Authorization', 'Bearer ' +AccessToken);
        req2.setbody('{"shared_link": {"access": "open"}}');
        Http http2 = new Http();
        HTTPResponse res2 = http2.send(req2);
        String Response2=res2.getBody();
        system.debug('Response2 '+Response2);
        Integer statusCode2=res.getStatusCode();
        // Parse JSON response to get Shared Link values.
        JSONParser parser2 = JSON.createParser(Response2);
        while(parser2.nextToken() != null) 
        {
            if((parser2.getCurrentToken() == JSONToken.FIELD_NAME))
            {
                String fieldName = parser2.getText();
                parser2.nextToken();
                if(fieldName == 'shared_link')
                {
                    system.debug('Enter shared_link ');
                    while(parser2.nextToken() != null) 
                    {
                        if((parser2.getCurrentToken() == JSONToken.FIELD_NAME))
                        {
                            String fieldName1 = parser2.getText();
                            parser2.nextToken();
                            if(fieldName1 == 'url')
                            {
                                system.debug('Enter url '+parser2.getText());
                                SharedLink = parser2.getText();
                            }
                        }
                    }
                }
            }
        }
        String s = SharedLink.substringAfter('s/');
        system.debug('s '+s);
        WLink = 'https://app.box.com/embed_widget/s/'+s+'?view=list&sort=name&direction=ASC&theme=blue';
        if(RefreshToken != null)
        {
            BoxCS.RefreshToken__c = RefreshToken ;
            update BoxCS;
        }
    }  
}

Here is the VF Page:

<apex:page standardController="Account" extensions="BoxAccountFolderWidgetController" action="{!WidgetMethod}" >    
    <iframe src="{!WidgetLink}" width="1000" height="400" frameborder="0" ></iframe>
</apex:page>

Test Class for above Controller:

@isTest
public class Test_BoxAccountFolderWidgetController {
    public static testmethod void test1()
    {
        Account ac = New Account (name ='TestAccount', Box_Folder_Id__c = '8644998269');
        insert ac;
        Apexpages.StandardController sss = new Apexpages.StandardController(ac);
        apexpages.currentpage().getparameters().put('id' , ac.id);
        BoxRefreshToken__c BoxCS = new BoxRefreshToken__c ( RefreshToken__c = 'AJtikYVgIUhEsvgPPnfPMLBvrhCtB3RCQFGon8TdWdxboJ1wt4XLUAyglMuqeVqF',
                                                           ClientId__c ='pgevke65b3i6ujpqbfmhpeh0b2tx7o6r',
                                                           ClientSecret__c = 'mwKeNUq8VARg6wIwzfLI84h47SLnlmnp');
        insert BoxCS;
        Map<string,string> Headers = new Map<string,string>();
        Headers.put('Content-Type', 'application/x-www-form-urlencoded');
        SingleRequestMock fakeResp = new SingleRequestMock(200,
                                                                  'Complete',
                                                                  '{"access_token":"YUBoKdFFSoosuj2xurAa2vnXqm6pUypB","expires_in":4084,"restricted_to":[],"refresh_token":"dWEDG768lQhtbIECGuYT5i9DCoq7Sd61ousFUD6Mro9FP2oxDmbU6arGdo8lXGan","token_type":"bearer"}',
                                                                  Headers);
        Test.startTest();
        Map<string,string> Headers1 = new Map<string,string>();
        Headers1.put('Content-Type', 'application/x-www-form-urlencoded');
        Headers1.put('Authorization', 'Bearer kCEBaUaNAfqvMenkBflDgqF22pBd5Gka');
        String Body1= '{"shared_link": {"access": "open"}}';
        SingleRequestMock fakeResp1 = new SingleRequestMock(200,
                                                                   'Complete',
                                                                   Body1,
                                                                   Headers1);
        Map<String, HttpCalloutMock> endpoint2TestResp = new Map<String,HttpCalloutMock>();
        endpoint2TestResp.put('https://api.box.com/oauth2/token',fakeResp);
        endpoint2TestResp.put('https://api.box.com/2.0/folders',fakeResp1);
        HttpCalloutMock multiCalloutMock =
            new MultiRequestMock(endpoint2TestResp);
        Test.setMock(HttpCalloutMock.class, multiCalloutMock);
        BoxAccountFolderWidgetController abc = new BoxAccountFolderWidgetController(sss);
        abc.WidgetMethod(); 
        Test.stopTest();
        //System.assertEquals(/*check for expected results here...*/);
    }
}

Any Help is appreciated.