Write Comprehensive Tests

@isTest
private class AccountHealthServiceTest {
    @isTest
    static void openCaseCountReflectsOnlyOpenCases() {
        Account acc = new Account(Name = 'Test Account');
        insert acc;

        insert new List<Case>{
            new Case(AccountId = acc.Id, Status = 'New'),
            new Case(AccountId = acc.Id, Status = 'New'),
            new Case(AccountId = acc.Id, Status = 'Closed')
        };

        AccountHealthService service = new AccountHealthService();
        System.assertEquals(2, service.getOpenCaseCount(acc.Id));
    }
}

1. @isTest — marks the test class.
2. private class AccountHealthServiceTest { — a dedicated test class for the service.
3. @isTest — marks the test method.
4. static void openCaseCountReflectsOnlyOpenCases() { — a name that states exactly what's being verified.
5. Account acc = new Account(Name = 'Test Account'); — test data, created fresh.
6. insert acc; — Module 19's DML, saving it.
7. (blank line)
8. insert new List<Case>{ — Module 25's bulk-insert style, three Cases at once.
9. new Case(AccountId = acc.Id, Status = 'New'), — an open Case.
10. new Case(AccountId = acc.Id, Status = 'New'), — a second open Case.
11. new Case(AccountId = acc.Id, Status = 'Closed') — a closed Case, deliberately included to prove it's excluded from the count.
12. }; — closes the list literal and the insert statement.
13. (blank line)
14. AccountHealthService service = new AccountHealthService(); — the class under test.
15. System.assertEquals(2, service.getOpenCaseCount(acc.Id)); — asserts the exact count, not just "greater than zero."
16. } — closes the test method.
17. } — closes the test class.

Two open Cases and one closed one, with a specific assertion of 2 — exactly Module 31's "assertions that actually tell you something" habit, verifying the exact expected count, not just "greater than zero."

@isTest
static void getHealthSummaryCombinesAllFourMetrics() {
    Account acc = new Account(Name = 'Test Account');
    insert acc;

    insert new Case(AccountId = acc.Id, Status = 'New');

    AccountHealthService service = new AccountHealthService();
    AccountHealthSummary summary = service.getHealthSummary(acc.Id);

    System.assertEquals(1, summary.openCaseCount);
    System.assertNotEquals(null, summary.averageResolutionDays);
    System.assertNotEquals(null, summary.totalWonRevenue);
}

1. @isTest — marks the test method.
2. static void getHealthSummaryCombinesAllFourMetrics() { — the name states the whole method's job.
3. Account acc = new Account(Name = 'Test Account'); — fresh test data.
4. insert acc; — saves it.
5. (blank line)
6. insert new Case(AccountId = acc.Id, Status = 'New'); — one open Case, enough to give the count a non-zero value to check.
7. (blank line)
8. AccountHealthService service = new AccountHealthService(); — the class under test.
9. AccountHealthSummary summary = service.getHealthSummary(acc.Id); — calls the combining method.
10. (blank line)
11. System.assertEquals(1, summary.openCaseCount); — the exact expected count.
12. System.assertNotEquals(null, summary.averageResolutionDays); — confirms the field was actually populated.
13. System.assertNotEquals(null, summary.totalWonRevenue); — same.
14. } — closes the test method.

This confirms getHealthSummary actually populates every field on the wrapper, not just that it runs without an exception.

@isTest
private class AccountHealthControllerTest {
    @isTest
    static void getAccountHealthReturnsExpectedSummary() {
        Account acc = new Account(Name = 'Test Account');
        insert acc;
        insert new Case(AccountId = acc.Id, Status = 'New');

        Test.startTest();
        AccountHealthSummary summary = AccountHealthController.getAccountHealth(acc.Id);
        Test.stopTest();

        System.assertEquals(1, summary.openCaseCount);
    }
}

1. @isTest — marks the test class.
2. private class AccountHealthControllerTest { — a dedicated test class for the controller.
3. @isTest — marks the test method.
4. static void getAccountHealthReturnsExpectedSummary() { — states what's verified.
5. Account acc = new Account(Name = 'Test Account'); — test data.
6. insert acc; — saves it.
7. insert new Case(AccountId = acc.Id, Status = 'New'); — one open Case for the summary to reflect.
8. (blank line)
9. Test.startTest(); — Module 31's governor-limit reset boundary.
10. AccountHealthSummary summary = AccountHealthController.getAccountHealth(acc.Id); — calls the controller method directly, exactly as an LWC would, not the service.
11. Test.stopTest(); — closes the boundary.
12. (blank line)
13. System.assertEquals(1, summary.openCaseCount); — confirms the whole chain produced the right answer.
14. } — closes the test method.
15. } — closes the test class.

Calling AccountHealthController.getAccountHealth directly — exactly as an LWC would — confirms the entire chain (controller → service → SOQL) works correctly end to end, not just the service layer in isolation.