Salesforce Apex Testing Assert Methods
Example
static TestMethod void DmlTest() {
List<Contact> allContacts = [SELECT Id FROM Contact];
System.assert(allContacts.isEmpty());
Contact testContact = new Contact(FirstName = 'John', LastName = 'Doe');
insert testContact;
allContacts = [SELECT Id FROM Contact];
System.assertNotEquals(0, allContacts.size(), 'Optional message in case of failure');
delete allContacts;
allContacts = [SELECT Id FROM Contact];
System.assertEquals(0, allContacts.size());
}
