In Spring ’15 release Salesforce has introduced new @testSetup annotation for Test class method. @testSetup annotation defined methods are used for creating common test records, and that records are available for all test methods in the class.

@testSetup methods create common test data easily and efficiently, and reduce test execution times especially when we are working with many records.

Example:

@iSTest
private class AccountControllerTest {
    
    //Test Setup Method
    @testsetup
    static void createAccount() {
        Account acc = new Account();
        acc.Name = 'Salesforce';
        insert acc;
    }
    
    //Test Method
    public static testMethod void test() {
        System.assertEquals(1, [SELECT COUNT() FROM Account Where Name = 'Salesforce']);
    }
}

Considerations:

• Records created by @testSetup method are available to all test methods in the test class.
• @testSetup methods are executed first in the test class before any test methods.
• One Test class can have only one @testSetup method. If multiple @testSetup method is written in a Test class then sequence of execution of those methods are not guaranteed.
• If the test class or a test method has access to organization data by using the @isTest(SeeAllData=true) annotation, test setup methods aren’t supported in this class.
• If any error occurss during the execution in @testSetup method, then entire test class fails.
• The data created by @testSetup methods will be rolled back after the completly execution of the test class.
• If a test setup method calls a non-test method of another class, no code coverage is calculated for the non-test method.