Test Classes
A test class is an Apex class that contains test methods—special methods that test your logic using the @isTest annotation, A test class is used to automatically check if your code works correctly. It helps find mistakes early, saves time, and makes sure changes don’t break anything.
Basic Structure
@isTest
private class SampleTestClass {
@isTest
static void sampleTestMethod() {
// 1. Prepare test data
// 2. Call method to test
// 3. Assert the result
}
}
Syntax Components Explained
| Part | Syntax | Explanation |
|---|---|---|
| Test Class | @isTest private class | @isTest tells Salesforce this is a test class. |
| Declaration | ClassNameTest | it’s not used in production logic |
| Test Method | @isTest static void | Marks a method as a test method. Must be static and return void. |
| Start/Stop/Test | Test.startTest() Test.stopTest() | Optional, but useful to separate setup from logic under test, and test governor limits. |
| Assertions | System.assert() System.assertEquals() | Used to compare expected vs actual results. Validates your logic. |
Example 1. Create an Account Record
Business Logic:
public class AccountService {
public static void createAccount(String accName) {
Account acc = new Account(Name = accName);
insert acc;
}
}
Explanation :
• A method createAccount takes a name and creates a new Account record in Salesforce.
• It sets the name of the account and inserts it into the database.
Test Class :
@isTest
private class AccountServiceTest {
@isTest
static void testCreateAccount() {
Test.startTest();
AccountService.createAccount(‘Acme Corp’);
Test.stopTest();
Account acc = [SELECT Name FROM Account WHERE Name = ‘Acme Corp’ LIMIT 1];
System.assertEquals(‘Acme Corp’, acc.Name);
}
}
Explanation :
• It checks if the createAccount method actually creates an account with the correct name.
• It uses System.assertEquals to validate that the inserted account has the correct name.
Run the Test Class:
1. Open Developer Console.
2. Click Test > New Run.
3. Select your test class (e.g., AccountServiceTest).
4. Click Run.
Check Results and Code Coverage,
After the test runs:
• You’ll see a Success or Failure status.
• You can open logs to debug failures.
• Check code coverage in the Developer Console:
• Click Test > Code Coverage > Show Code Coverage.
• It highlights covered lines in blue, uncovered in red.
Expected Output :
• Test will pass if the account is created with the name “Acme Corp”.
• System.assertEquals(‘Acme Corp’, acc.Name) will be true.
Test Result :
testCreateAccount — PASS
Example 2. Handling Missing Required Fields (Negative Test)
Business Logic :
public class ContactHandler {
public static void createContact(String lastName) {
if (String.isEmpty(lastName)) {
throw new IllegalArgumentException(‘Last Name is required’);
}
Contact c = new Contact(LastName = lastName);
insert c;
}
}
Explanation :
• It creates a contact only if the last name is provided.
• If the last name is empty, it throws an error.
Test Class:
@isTest
private class ContactHandlerTest {
@isTest
static void testCreateContact_MissingLastName() {
try {
ContactHandler.createContact(”);
System.assert(false, ‘Expected exception was not thrown’);
} catch (Exception e) {
System.assert(e.getMessage().contains(‘Last Name is required’));
}
}
}
Explanation :
• It tries to create a contact without a last name to see if the system throws an error.
• It checks that the correct error message is returned.
Expected Output :
• Test will pass if an exception is thrown with message “Last Name is required”.
• System.assert inside catch block will be true.
Test Class:
testCreateContact_MissingLastName — PASS
Example 3. Updating a Record
Business Logic :
public class AccountUpdater {
public static void updateIndustry(Id accountId, String newIndustry) {
Account acc = [SELECT Id, Industry FROM Account WHERE Id = :accountId];
acc.Industry = newIndustry;
update acc;
}
}
Explanation :
• It finds an account by ID and updates its Industry field.
Test Class :
@isTest
private class AccountUpdaterTest {
@isTest
static void testUpdateIndustry() {
Account acc = new Account(Name = ‘Tech Co’);
insert acc;
Test.startTest();
AccountUpdater.updateIndustry(acc.Id, ‘Technology’);
Test.stopTest();
Account updated = [SELECT Industry FROM Account WHERE Id = :acc.Id];
System.assertEquals(‘Technology’, updated.Industry); }
}
Explanation:
• Test will pass if the Industry field of the account is updated to “Technology”.
Test Result :
✔ testUpdateIndustry — PASS
Example 4. Testing a Trigger
Trigger:
trigger AccountTrigger on Account (before insert) {
for (Account acc : Trigger.new) {
if (acc.Industry == null) {
acc.Industry = ‘Default’;
}
}
}
Explanation :
• Before an account is inserted, it checks if the Industry is missing.
• If it’s missing, it automatically sets it to “Default”.
Test Class:
@isTest
private class AccountTriggerTest {
@isTest
static void testTriggerAssignsDefaultIndustry() {
Account acc = new Account(Name = ‘Auto Co’);
insert acc;
Account result = [SELECT Industry FROM Account WHERE Id = :acc.Id];
System.assertEquals(‘Default’, result.Industry);
}
}
Explanation :
• It creates an account without specifying Industry.
• It then checks whether the trigger automatically set Industry to “Default”.
Expected Output :
• Test will pass if an account is created with no industry and the trigger assigns “Default”.
Test Result:
✔ testTriggerAssignsDefaultIndustry — PASS
Best Practices for Apex Testing
• Use meaningful test method names
• Cover positive, negative, and edge cases
• Use System.assert to validate behavior
• Avoid using real org data – always create test data
• Keep tests fast and isolated
Tasks For Practice
1. Create a class AccountManager with a method createAccount that takes an account name and creates an Account record.
Write a test class that verifies the account is created with the correct name.
2. Write a before-insert trigger on Contact that assigns “No Email” to the Email field if it is blank.
Write a test class that verifies the trigger assigns this default.
3. Write a method in LeadService that inserts a Lead but throws an exception if the Company field is blank.
Write a test to check that the exception is thrown when Company is blank.
4. Create a class ContactUpdater with a method that updates a Contact’s Phone number by Id.
Write a test to verify the phone number is updated correctly.
