generating-apex-test

SKILL.md

Generating Apex Tests

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

Core Principles

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

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

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

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

Use Assert class only — Assert.areEqual, Assert.isTrue, Assert.fail, etc. Never use legacy System.assert, System.assertEquals, or System.assertNotEquals

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

Test negative paths — validate error handling and exception scenarios, not just happy paths

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():