Carry out the following steps to create an Apex test class, that provides unit test coverage for our Apex Controller, using the Salesforce Developer Console:

1. Click on the Setup gear icon, as shown in the following screenshot:

The Setup gear icon is located in the top right-hand area of the main Home page.

2. Click the Developer Console option, as shown in the following screenshot:

3. In the resulting Developer Console window, click on File.
4. Click on New.
5. Click on Apex Class, as shown in the following screenshot:

6. In the resulting New Apex class dialog, enter AccountSearchControllerTest in the Please enter a name for your new Apex class textbox.
7. Click on OK, as shown in the following screenshot:

8. In the resulting Apex class edit page, paste the following code:

@isTest 
private class AccountSearchControllerTest{ 
 
  @isTest 
  static void test_getAccounts(){ 
 
  // Create test data 
  List<Account> lstAccTestData = new List<Account>{}; 
 
  // Create test data 
  for(Integer i = 5; i < 10; i++){ 
  Account acc = new Account(Name = 'Test Account ' + i); 
  lstAccTestData .add(acc); 
  } 
 
  Test.startTest(); 
  List<Account> lstAccResult = new List<Account>{}; 
 
  // Test Account Does Not exist 
  String sNonExistingAccount = 'Non Existing Account'; 
  lstAccResult =
  AccountSearchController.getAccounts(sNonExistingAccount); 
  System.assertEquals(null, lstAccResult); 
 
  // Test Account Does Exist 
  String sDoesExistAccount = 'Test Account'; 
  lstAccResult =
  AccountSearchController.getAccounts(sDoesExistAccount); 
  System.assertNotEquals(null, lstAccResult); 
 
  Test.stopTest(); 
 
  } 
} 
 

9. Click on File.
10. Click on Save, as shown in the following screenshot: