Please guide me for getting full code coverage for the following class by using best practices,

public class sendemail_torelated_contacts
{

list<string>emailids;
public PageReference sendemail()
{
emailids=new list<string>();
for(contact c:conlst)
{
if(c.email!=null)
{
emailids.add(c.email);
}
}

system.debug('-----------------------------------------------'+emailids.size());
if(emailids.size()>0)
{
Messaging.SingleEmailMessage mail = new Messaging.SingleEmailMessage();

mail.setToAddresses(emailids);

mail.setSubject('Test Mail');

mail.setUseSignature(false);
mail.setHtmlBody('This is a test mail');

// Send the email
Messaging.sendEmail(new Messaging.SingleEmailMessage[] { mail });

ApexPages.Message myMsg = new ApexPages.Message(ApexPages.Severity.INFO, 'Mail sent successfully');
apexpages.addmessage(myMsg);
}else
{
ApexPages.Message myMsg = new ApexPages.Message(ApexPages.Severity.warning, 'NO Destination found');
apexpages.addmessage(myMsg);
}

return null;
}

public PageReference find_contacts()
{
//system.debug('=================================='+accid);
conlst=new contact[]{};
if(accid!='')
{
conlst=[select id,accountid,name,email,phone from contact where accountid=:accid];
}
if(conlst.size()>0)
{
showbtn=true;
}else
{
showbtn=false;
}
return null;
}

public String accid { get; set; }
public boolean showbtn{get;set;}

account[]acclst;
public contact[]conlst{get;set;}


public account[] getaccounts()
{
acclst=new account[]{};
acclst=[select id,name,phone from account where name in('appshark','ibm','infosys')];

return acclst;

}

//Test method for code coverage-----------------------

Private static testmethod void test()
{
account a=new account(name='test',phone='09030182818');
insert a;
contact con=new contact(lastname='testcon',email='vasu.takasi@test.com',accountid=a.id);
insert con;
sendemail_torelated_contacts obj=new sendemail_torelated_contacts();
obj.showbtn=true;
obj.conlst=new contact[]{};
obj.conlst.add(con);
obj.getaccounts();
obj.find_contacts();
obj.sendemail();

}

}