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- use-generateguid-for-unique-test-fixture-values.md: narrowed the collision rule to primary-key/unique-lookup fields - an ordinary descriptive field carries no uniqueness constraint, so a hardcoded or deterministic value there isn't the anti-pattern (the article and its al-testing-review.md worklist cue both said "primary-key or descriptive field"). Also corrected GenerateRandomCode: it opens its target table as a temporary RecordRef that starts and stays empty, so its repeat/until loop always exits after one iteration and never retries even within a single test run - the "non-colliding within a test run" claim was false. It's the rightmost N characters of GenerateGUID()'s sequential series, so a short field's value cycles (Code[1] repeats every 10 calls, Code[2] every 100). Verified against LibraryUtility.Codeunit.al in the BCApps reference clone. - item-ledger-entry-document-no-follows-last-shipping-no: both fixtures called FindSet() without consuming its optional Boolean, which raises a runtime error on an empty result set - the opposite of the article's own claimed "silently matches zero rows, no error" behavior. Wrapped in `if ... then;` per the existing guard-database-reads.good.al idiom. - al-data-modeling-review.md: widened both not-applicable scope clauses (intro and outcome) to include dimension wiring, posting- routine structure, and Item Ledger Entry document-number lookups - the leaf declared itself not-applicable outside setup/master/key/ numbering/block/audit surfaces despite having a targeted cue for this PR's own new article. - Converted this PR's 8 plain-backtick "See sample: `x.good.al`." references (across all 4 new articles) to the READ-convention markdown-link form required by Knowledge-Retrieval.ps1. Rebased onto upstream/main (one conflict in al-data-modeling-review.md intro wording, merged).
33 lines
4.1 KiB
Markdown
33 lines
4.1 KiB
Markdown
---
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bc-version: [all]
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domain: testing
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keywords: [generateguid, library-utility, test-fixtures, uniqueness, generaterandomcode, maxstrlen]
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technologies: [al]
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countries: [w1]
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application-area: [all]
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---
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# Generate unique test fixture values with LibraryUtility helpers, not hardcoded literals
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## Description
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A fixture helper that assigns a hardcoded literal to a primary-key field, or to any field the test relies on as a unique lookup identifier, 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. An ordinary descriptive field carries no such constraint: two rows with the same description do not collide on insert, and a deterministic descriptive value is often exactly what an exact-match assertion needs, so none of this applies to it. `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.
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## Best Practice
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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:
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- `GenerateRandomCode(FieldNo, TableNo)` opens the target table as a **temporary** `RecordRef`: the buffer starts and stays empty, so its `repeat...until RecRef.IsEmpty()` loop always exits after one iteration — despite taking `TableNo`, it never checks the real table, and it never retries even within its own call. Its value is the rightmost `FieldRef.Length` characters of `GenerateGUID()`'s sequential `GU00000000`–`GU99999999` series, so for a short field that window of digits cycles: a 1-character field repeats every 10 calls, a 2-character field every 100, and so on. It is a finite short-field namespace with a low collision *chance* within one test run — not a guarantee at any scope, unlike the table-checking helpers below.
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- `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.
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- `GenerateRandomCode20(FieldNo, TableNo)` is the same real, verified-against-the-table pattern as `GenerateRandomCodeWithLength`, sized for a `Code[20]` field.
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- `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.
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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.
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See sample: [`use-generateguid-for-unique-test-fixture-values.good.al`](use-generateguid-for-unique-test-fixture-values.good.al).
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## Anti Pattern
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Hardcoding a primary-key or unique-lookup fixture value such as `'TEST001'`, which collides across parallel or repeated test runs — a fixed descriptive value is not this anti-pattern, since the field carries no uniqueness constraint. 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.
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See sample: [`use-generateguid-for-unique-test-fixture-values.bad.al`](use-generateguid-for-unique-test-fixture-values.bad.al).
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