bcquality/microsoft/knowledge/testing/use-library-codeunits-for-test-fixtures.md
Jesper Schulz-Wedde 373ec31e2e Address review: merge handler articles, adopt enqueue-driven pattern
Respond to @nikolakukrika's review on #62:

- Merge ui-calls-require-test-handlers, handlerfunctions-attribute-must-match-ui-path
  and handlers-enqueue-never-assert into a single ui-handlers-in-tests article.
- Adopt the enqueue-from-test / dequeue-and-assert-in-handler pattern using
  Assert.ExpectedConfirm/ExpectedMessage (substring match), with Initialize()
  clearing LibraryVariableStorage and AssertEmpty() proving exact call counts.
- asserterror sample now uses Assert.ExpectedTestFieldError + FieldCaption instead
  of hardcoded message/code; article text points to the library helpers.
- Drop the tablerelation article and fold its test-relevant ordering point
  (relations checked on Validate/Insert(true); build parents first) into
  use-library-codeunits-for-test-fixtures.

Article count 198 -> 195.

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
2026-07-07 09:29:32 +02:00

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---
bc-version: [all]
domain: testing
keywords: [library-codeunits, fixtures, test-data, number-series, prerequisite]
technologies: [al]
countries: [w1]
application-area: [all]
---
# Build fixtures with the test Library codeunits, not hand-rolled Init/Insert
## Description
BC ships a layer of test Library codeunits — `LibrarySales`, `LibraryPurchase`, `LibraryERM`, `LibraryInventory`, `LibraryRandom` and many more — whose job is to create valid records. `CreateCustomer` assigns a number from the customer number series, fills the mandatory fields, and satisfies the table relations the platform enforces; `CreateItem` does the same for items. Hand-rolling `Customer.Init`/`Customer.Insert` with invented values skips the number series and any field a future app version adds as mandatory, so the fixture is invalid the moment it is created and rots silently as the schema evolves. The library codeunits also encode fixture *ordering*: because a `TableRelation` field is checked on `Validate` and `Insert(true)`, every parent a foreign key points to must already exist when the dependent record is built. Assemble fixtures top-down — customer and item before the sales line that references them — or the relation check aborts the test at runtime with a data error rather than an assertion. Prefer the Library codeunits for prerequisite data: they encode the setup the platform requires and are maintained alongside the base app.
## Best Practice
Reach for the matching Library codeunit before writing manual record setup: `LibrarySales.CreateCustomer`, `LibrarySales.CreateSalesHeader`/`CreateSalesLine`, `LibraryInventory.CreateItem`, `LibraryERM.CreateGLAccount`, and `LibraryRandom.RandInt`/`RandDec` for values. Create the prerequisite parents first and reference their primary keys from dependent records, and `Validate` the foreign-key field so the `TableRelation` — and any field-validation logic — runs exactly as it would in production. Pass the records they return into the code under test. The fixtures stay valid across upgrades because the library — not your test — owns the knowledge of what a well-formed record requires.
See sample: `use-library-codeunits-for-test-fixtures.good.al`.
## Anti Pattern
`Customer.Init(); Customer."No." := 'X'; Customer.Insert();` — a record with a hand-picked primary key, no number-series entry, and none of the mandatory fields a real customer needs. It compiles and may even insert, but it bypasses setup the production code assumes, and it breaks the first time the schema gains a required field the test does not know about.
See sample: `use-library-codeunits-for-test-fixtures.bad.al`.