bcquality/microsoft/knowledge/testing/testisolation-belongs-on-the-test-runner.md

bc-version	domain	keywords	technologies	countries	application-area
all	testing	testisolation testrunner autocommit commit rollback test-order database-state	al	w1	all

Configure TestIsolation on the test runner

Description

TestIsolation is a property of a Subtype = TestRunner codeunit, not of the test codeunit being executed. Its default is Disabled. Codeunit rolls back database changes after each test codeunit and Function after each test method, including changes that the code under test explicitly committed. Without runner isolation, an AutoCommit test can leave data behind and make later tests order-dependent.

Best Practice

Run independent suites with TestIsolation = Codeunit or Function, choosing the narrowest boundary the runner supports. Pair this with the appropriate method-level TransactionModel: AutoCommit permits code under test to commit, while runner isolation still restores the database afterward. Keep isolation disabled only for an intentionally shared-state suite whose ordering and cleanup are explicit.

See sample: testisolation-belongs-on-the-test-runner.good.al.

Anti Pattern

An AutoCommit test exercises committed writes under a test runner that omits TestIsolation or sets it to Disabled, then assumes the database is restored automatically. This article owns runner-level rollback; transactionmodel-attribute-governs-test-transactions.md separately owns the method attribute.

See sample: testisolation-belongs-on-the-test-runner.bad.al.