How to test future methods in test class in Salesforce?

To test methods defined with the future annotation, call the class containing the method in a startTest(), stopTest()code block. All asynchronous calls made after the startTest method are collected by the system. When stopTest is executed, all asynchronous processes are run synchronously.
@isTest
private class FutureApexTest {
private static testMethod void callFutureMethod() {
Test.startTest();
// Call your @future method here.
FutureApex.doCallFuture();
// Now that we’ve queued up the @future method to be executed, we
// need to call Test.stopTest(). When Test.stopTest() runs, all
// queued and scheduled Apex that would occur in the future is actually
// executed immediately at this time.
Test.stopTest();
// Validate the expected results.
System.assertEquals(expectedValue, actualValue);
}
}