---
bc-version: [all]
domain: testing
keywords: [generateguid, library-utility, test-fixtures, uniqueness, generaterandomcode, maxstrlen]
technologies: [al]
countries: [w1]
application-area: [all]
---

# Generate unique test fixture values with LibraryUtility helpers, not hardcoded literals

## Description

A fixture helper that assigns a hardcoded literal to a primary-key or descriptive field collides the moment two tests, or two runs of the same test, create that fixture without cleanup, and a literal longer than the field allows raises a truncation or insert error. `LibraryUtility.GenerateGUID()` is not a real GUID — it is a `Code[10]` number-series value (`GU00000000`–`GU99999999`) — and it returns the full 10 characters unshortened. Truncating it yourself with `CopyStr(..., 1, MaxStrLen(ShorterField))` for a field under 10 characters is unsafe: the changing digits sit at the right end and are exactly what gets cut off, so consecutive calls into a short field can produce the same truncated value. `GenerateGUID()` is only safe as-is for a field that holds the full 10 characters.

## Best Practice

For a field that holds the full 10 characters, assign `LibraryUtility.GenerateGUID()` directly. For a shorter field, do not truncate a GUID yourself — but also do not assume every `LibraryUtility` helper verifies uniqueness against the real table, because they don't all behave the same way:

- `GenerateRandomCode(FieldNo, TableNo)` opens the target table as a **temporary** `RecordRef`, so its own emptiness check never inspects real rows — despite taking `TableNo`, it does not verify against the actual table. It's safe to use for its non-colliding-*within-a-single-test-run* value (derived from `GenerateGUID()`'s own number series), not for a guarantee against pre-existing or leftover data.
- `GenerateRandomCodeWithLength(FieldNo, TableNo, CodeLength)` opens the real (non-temporary) table and loops until the generated value doesn't collide — a genuine verified-unique guarantee — but it returns `Code[10]` regardless of the requested `CodeLength`, so it's only useful for a field of 10 characters or fewer.
- `GenerateRandomCode20(FieldNo, TableNo)` is the same real, verified-against-the-table pattern as `GenerateRandomCodeWithLength`, sized for a `Code[20]` field.
- `GenerateRandomXMLText(Length)` performs no table lookup at all — it's a plain random-text generator, appropriate for a descriptive/incidental field where uniqueness doesn't matter, not for a value that needs to be collision-checked.

Pick `GenerateRandomCodeWithLength`/`GenerateRandomCode20` when the test genuinely needs a code verified unique against the table; use `GenerateRandomCode`/`GenerateGUID`/`GenerateRandomXMLText` for incidental values where a low collision *chance* is enough.

See sample: `use-generateguid-for-unique-test-fixture-values.good.al`.

## Anti Pattern

Hardcoding a fixture value such as `'TEST001'` or a short descriptive literal, which collides across parallel or repeated test runs. Equally an anti-pattern: truncating `GenerateGUID()`'s result with `CopyStr(..., 1, MaxStrLen(Field))` for a field shorter than 10 characters — the truncation removes the part of the value that actually varies.

See sample: `use-generateguid-for-unique-test-fixture-values.bad.al`.