/platform-apex-test-generate

name: platform-apex-test-generate
description: "Use to generate and validate Apex test classes with TestDataFactory patterns, bulk testing (251+ records), mocking, assertions, and disciplined test-fix loops. Use when creating Apex test classes (for triggers, services, controllers, batch jobs, queueables, and callouts), improving coverage, debugging or fixing failing Apex tests, or running test/coverage analysis. Triggers on *Test.cls files, sf apex run test, coverage reports. Do NOT trigger for production Apex (use platform-apex-generate) or Jest/LWC tests."
metadata:
  version: "1.1"
  domains: ["Platform"]
  minApiVersion: "66.0"
  relatedSkills:
    - "platform-apex-generate"
  cliTools:
    - tool: ["sf"]
      semver: ">=2.0.0"

Generating Apex Tests

Generate production-ready Apex test classes and run disciplined test-fix loops with coverage analysis.

Core Principles

1. **One behavior per method** — each test method validates a single scenario. Separate positive, negative, and bulk tests. NEVER combine related-but-distinct inputs (e.g., null and empty) in one method — create `_NullInput_` and `_EmptyInput_` as separate test methods 2. **Bulkify tests** — test with 251+ records to cross the 200-record trigger batch boundary. **Batch Apex exception:** in test context only one `execute()` invocation runs, so set `batchSize >= testRecordCount`. See [references/async-testing.md](references/async-testing.md) 3. **Isolate test data** — every `@TestSetup` must delegate record creation to a `TestDataFactory` class. If none exists, create one first. Never build record lists inline in `@TestSetup`. Never rely on org data (`SeeAllData=false`) or hardcoded IDs. For duplicate rule handling, see [references/test-data-factory.md](references/test-data-factory.md) 4. **Assert meaningfully** — use exact expected values computed from test data setup. NEVER use range assertions or approximate counts when the value is deterministic. Always include failure messages. See [references/assertion-patterns.md](references/assertion-patterns.md) 5. **Use `Assert` class only** — `Assert.areEqual`, `Assert.isTrue`, `Assert.fail`, etc. Never use legacy `System.assert`, `System.assertEquals`, or `System.assertNotEquals` 6. **Mock external boundaries** — use `HttpCalloutMock` for callouts, `Test.setFixedSearchResults` for SOSL, DML mock classes for database isolation. Design for testability via constructor injection. See [references/mocking-patterns.md](references/mocking-patterns.md) 7. **Test negative paths** — validate error handling and exception scenarios, not just happy paths 8. **Wrap with start/stop** — pair `Test.startTest()` with `Test.stopTest()` to reset governor limits and force async execution

Test.startTest() / Test.stopTest()

Always wrap the code under test in `Test.startTest()` / `Test.stopTest()`:

• Resets governor limits so the test measures only the code under test
• Executes async operations synchronously (queueables, batch, future methods)
• Fires scheduled jobs immediately

Test Code Anti-Patterns

| Anti-Pattern | Fix | |---|---| | SOQL/DML inside loops | Query once before the loop; use `Map<Id, SObject>` for lookups | | Magic numbers in assertions | Derive expected values from setup constants | | God test class (>500 lines) | Split into multiple test classes by behavior area | | Long test methods (>30 lines) | Extract Given/When/Then into helper methods | | Generic `Exception` catch | Catch the specific expected type (e.g., `DmlException`) |

Workflow

Step 1 — Gather Context

Before generating or fixing tests, identify:

• the target production class(es) under test
• existing test classes, test data factories, and setup helpers
• desired test scope (single class, specific methods, suite, or local tests)
• coverage threshold (75% minimum for deploy, 90%+ recommended)
• org alias when running tests against an org

Step 2 — Generate the Test Class

Apply the structure, naming conventions, and patterns from the asset templates and reference docs.

**MANDATORY — File Deliverables:** For every test class, create BOTH files: 1. `{ClassName}Test.cls` — the test class (use [assets/test-class-template.cls](assets/test-class-template.cls) as starting point) 2. `{ClassName}Test.cls-meta.xml` — the metadata file:

<?xml version="1.0" encoding="UTF-8"?>
<ApexClass xmlns="http://soap.sforce.com/2006/04/metadata">
    <apiVersion>66.0</apiVersion>
    <status>Active</status>
</ApexClass>

If no `TestDataFactory` exists in the project, create `TestDataFactory.cls` + `TestDataFactory.cls-meta.xml` using [assets/test-data-factory-template.cls](assets/test-data-factory-template.cls).

@TestSetup Example

@TestSetup
static void setupTestData() {
    List<Account> accounts = TestDataFactory.createAccounts(251, true);
}

Test Method Structure

Use Given/When/Then:

@isTest
static void shouldUpdateStatus_WhenValidInput() {
    // Given
    List<Account> accounts = [SELECT Id FROM Account];

    // When
    Test.startTest();
    MyService.processAccounts(accounts);
    Test.stopTest();

    // Then
    List<Account> updated = [SELECT Id, Status__c FROM Account];
    Assert.areEqual(251, updated.size(), 'All accounts should be processed');
}

Negative Test — Exception Pattern

Use try/catch with `Assert.fail` to verify expected exceptions:

@isTest
static void shouldThrowException_WhenInvalidInput() {
    // Given
    List<Account> emptyList = new List<Account>();

    // When/Then
    Test.startTest();
    try {
        MyService.processAccounts(emptyList);
        Assert.fail('Expected MyCustomException to be thrown');
    } catch (MyCustomException e) {
        Assert.isTrue(e.getMessage().contains('cannot be empty'),
            'Exception message should indicate empty input');
    }
    Test.stopTest();
}

Naming Convention

• `should[ExpectedResult]_When[Scenario]`: `shouldSendNotification_WhenOpportunityClosed