Write Test Class for Trigger: Complete Guide | SalesforceTutorial

Writing test classes for Apex triggers is mandatory for deployment to production. Every trigger requires at least 75% code coverage, and test classes must validate both positive and negative scenarios. This guide covers trigger test patterns, schedulable class testing, batch class coverage, and proper use of System.assertEquals assertions.

Basic Test Class Structure for Triggers

A trigger test class follows the standard Apex test pattern with @isTest annotation and testMethod declarations. The test must create test data, execute the trigger logic, and assert expected outcomes using System.assertEquals or similar assertion methods.

Apex Trigger Code:

trigger accountAfterInsert on Account (after insert) {

	string managerId= [Select Id, ManagerId FROM User WHERE Id = :userInfo.getUserId()].ManagerId;

	for(Account acc: trigger.New){
		AccountShare accShare = new AccountShare();
		accShare .ParentId = acc.Id;
		accShare .UserOrGroupId = managerId;
		accShare .AccessLevel = 'EDIT';
		accShare .RowCause = Schema.accountShare.RowCause.Manual;
	}
}

// Unit Test for above Trigger

@isTest
private class AccountTriggersTest{
	private static testmethod void accountTriggersTest(){
		Account acc = new Account();
		acc.name = 'NewAccount';
		acc.address = 'USA';
		insert acc;
	}
}

Enhanced Test Class with System.assertEquals Assertions

The basic example above lacks proper assertions and error handling. A production-ready test class must verify the trigger’s behavior using System.assertEquals and handle edge cases.

@isTest
private class AccountTriggersTest {
    
    @testSetup
    static void setupTestData() {
        // Create test users with manager hierarchy
        Profile standardProfile = [SELECT Id FROM Profile WHERE Name = 'Standard User' LIMIT 1];
        
        User manager = new User(
            FirstName = 'Test',
            LastName = 'Manager',
            Email = 'testmanager@example.com',
            Username = 'testmanager@example.com.test',
            Alias = 'tmgr',
            ProfileId = standardProfile.Id,
            TimeZoneSidKey = 'America/New_York',
            LocaleSidKey = 'en_US',
            EmailEncodingKey = 'UTF-8',
            LanguageLocaleKey = 'en_US'
        );
        insert manager;
        
        User testUser = new User(
            FirstName = 'Test',
            LastName = 'User',
            Email = 'testuser@example.com',
            Username = 'testuser@example.com.test',
            Alias = 'tuser',
            ProfileId = standardProfile.Id,
            ManagerId = manager.Id,
            TimeZoneSidKey = 'America/New_York',
            LocaleSidKey = 'en_US',
            EmailEncodingKey = 'UTF-8',
            LanguageLocaleKey = 'en_US'
        );
        insert testUser;
    }
    
    @isTest
    static void testAccountTriggerPositive() {
        // Get test user with manager
        User testUser = [SELECT Id, ManagerId FROM User WHERE Username = 'testuser@example.com.test' LIMIT 1];
        
        System.runAs(testUser) {
            Test.startTest();
            
            // Create account to trigger the sharing logic
            Account testAccount = new Account(
                Name = 'Test Account',
                BillingStreet = '123 Main St',
                BillingCity = 'New York',
                BillingState = 'NY',
                BillingCountry = 'USA'
            );
            insert testAccount;
            
            Test.stopTest();
            
            // Verify AccountShare record was created
            List shares = [SELECT Id, ParentId, UserOrGroupId, AccessLevel 
                                       FROM AccountShare 
                                       WHERE ParentId = :testAccount.Id 
                                       AND RowCause = 'Manual'];
            
            System.assertEquals(1, shares.size(), 'Expected one AccountShare record');
            System.assertEquals(testUser.ManagerId, shares[0].UserOrGroupId, 'Manager should have access');
            System.assertEquals('Edit', shares[0].AccessLevel, 'Access level should be Edit');
        }
    }
    
    @isTest
    static void testAccountTriggerNoManager() {
        // Test scenario where user has no manager
        User userNoManager = [SELECT Id FROM User WHERE Username = 'testmanager@example.com.test' LIMIT 1];
        
        System.runAs(userNoManager) {
            Test.startTest();
            
            try {
                Account testAccount = new Account(
                    Name = 'Test Account No Manager',
                    BillingCountry = 'USA'
                );
                insert testAccount;
                
                // Verify no sharing records created when manager is null
                List shares = [SELECT Id FROM AccountShare 
                                           WHERE ParentId = :testAccount.Id 
                                           AND RowCause = 'Manual'];
                System.assertEquals(0, shares.size(), 'No shares should be created without manager');
                
            } catch (Exception e) {
                // Handle potential null pointer exceptions gracefully
                System.assert(e.getMessage().contains('null'), 'Expected null manager error');
            }
            
            Test.stopTest();
        }
    }
}

Test Class for Schedulable Apex Classes

Schedulable classes require different test patterns since they execute asynchronously. Use Test.startTest() and Test.stopTest() to force synchronous execution in tests.

// Example Schedulable Class
public class AccountCleanupSchedulable implements Schedulable {
    public void execute(SchedulableContext sc) {
        AccountCleanupBatch batch = new AccountCleanupBatch();
        Database.executeBatch(batch, 200);
    }
}

// Test Class for Schedulable Class
@isTest
private class AccountCleanupSchedulableTest {
    
    @isTest
    static void testSchedulableExecution() {
        Test.startTest();
        
        // Schedule the job
        String cronExp = '0 0 0 1 1 ? 2025';
        String jobId = System.schedule('Test Account Cleanup', cronExp, new AccountCleanupSchedulable());
        
        // Verify job was scheduled
        CronTrigger ct = [SELECT Id, CronExpression, TimesTriggered, NextFireTime 
                         FROM CronTrigger WHERE Id = :jobId];
        
        System.assertEquals(cronExp, ct.CronExpression, 'Cron expression should match');
        System.assertEquals(0, ct.TimesTriggered, 'Job should not have run yet');
        
        Test.stopTest();
        
        // After Test.stopTest(), scheduled job executes synchronously
        // Verify batch job was queued (implementation depends on batch logic)
    }
}

Test Class for Batch Apex Classes

Batch classes require testing the start, execute, and finish methods separately. Create test data within governor limits and verify batch processing logic.

// Example Batch Class
public class AccountCleanupBatch implements Database.Batchable {
    
    public Database.QueryLocator start(Database.BatchableContext bc) {
        return Database.getQueryLocator(
            'SELECT Id, Name FROM Account WHERE LastModifiedDate < LAST_N_DAYS:365'
        );
    }
    
    public void execute(Database.BatchableContext bc, List accounts) {
        delete accounts;
    }
    
    public void finish(Database.BatchableContext bc) {
        // Send completion email or other cleanup
        System.debug('Batch completed: ' + bc.getJobId());
    }
}

// Test Class for Batch Class
@isTest
private class AccountCleanupBatchTest {
    
    @testSetup
    static void setupTestData() {
        List oldAccounts = new List();
        for (Integer i = 0; i < 200; i++) {
            oldAccounts.add(new Account(
                Name = 'Old Account ' + i,
                BillingCountry = 'USA'
            ));
        }
        insert oldAccounts;
        
        // Update LastModifiedDate to simulate old records
        Test.setCreatedDate(oldAccounts[0].Id, Date.today().addDays(-400));
    }
    
    @isTest
    static void testBatchExecution() {
        Test.startTest();
        
        AccountCleanupBatch batch = new AccountCleanupBatch();
        Id jobId = Database.executeBatch(batch, 100);
        
        Test.stopTest();
        
        // Verify batch job completed
        AsyncApexJob job = [SELECT Id, Status, NumberOfErrors, JobItemsProcessed 
                           FROM AsyncApexJob WHERE Id = :jobId];
        
        System.assertEquals('Completed', job.Status, 'Batch should complete successfully');
        System.assertEquals(0, job.NumberOfErrors, 'No errors expected');
        
        // Verify records were processed (actual deletion depends on test data age)
        List remainingAccounts = [SELECT Id FROM Account];
        System.assert(remainingAccounts.size() >= 0, 'Batch should process accounts');
    }
}

System.assertEquals Best Practices in Test Classes

System.assertEquals validates expected vs actual values in test methods. Always include meaningful assertion messages for debugging failed tests.

Common System.assertEquals Patterns

• Basic assertion: System.assertEquals(expected, actual, 'Error message')
• List size: System.assertEquals(5, accounts.size(), 'Should create 5 accounts')
• Field values: System.assertEquals('Active', account.Status__c, 'Status should be Active')
• Boolean checks: System.assertEquals(true, account.IsActive__c, 'Account should be active')
• Null checks: System.assertEquals(null, account.ManagerId, 'Manager should be null')

Alternative Assertion Methods

• System.assertNotEquals() – Verify values are different
• System.assert() – Boolean condition testing
• System.assertNotEquals(null, value) – Verify non-null values

Governor Limits and Test Class Considerations

Test classes must respect Salesforce governor limits even in test context. Key limits for trigger testing:

• SOQL queries: 100 per transaction (synchronous)
• DML statements: 150 per transaction
• Records per DML: 10,000 maximum
• CPU time: 10,000ms synchronous, 60,000ms asynchronous
• Heap size: 6MB synchronous, 12MB asynchronous

Use @testSetup methods to create test data once and share across test methods. This reduces DML statements and improves test performance.

Common Test Class Errors and Solutions

MIXED_DML_OPERATION Error

Occurs when mixing setup and non-setup object DML in the same transaction. Solution: Use System.runAs() or separate transactions.

// Incorrect - causes MIXED_DML_OPERATION
User testUser = new User(/* user fields */);
insert testUser;
Account testAccount = new Account(Name = 'Test');
insert testAccount; // Error here

// Correct - separate transactions
System.runAs(new User(Id = UserInfo.getUserId())) {
    User testUser = new User(/* user fields */);
    insert testUser;
}
Account testAccount = new Account(Name = 'Test');
insert testAccount;

Insufficient Code Coverage

Ensure test methods exercise all trigger scenarios: insert, update, delete, undelete. Cover both positive and negative test cases.

Frequently Asked Questions