Add testing knowledge: UI handlers, table relations, asserterror, fixtures (P1+P2) (#62)

* Add testing knowledge: UI handlers, table relations, asserterror, fixtures (P1+P2)

Six BC-specific testing-domain knowledge articles in community/knowledge/testing/, each with .good.al/.bad.al samples:

- ui-calls-require-test-handlers
- tablerelation-requires-prerequisite-records
- handlers-enqueue-never-assert
- handlerfunctions-attribute-must-match-ui-path
- asserterror-needs-expectederror-and-code
- use-library-codeunits-for-test-fixtures

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Move testing knowledge from community to microsoft layer

Relocates the six P1+P2 testing-domain articles (18 files: .md + .good.al + .bad.al each) from community/knowledge/testing/ to microsoft/knowledge/testing/ per maintainer request. Pure git-mv rename; no content or frontmatter changes.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* 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>

---------

Co-authored-by: Jesper Schulz-Wedde <jesper.schulzwedde@microsoft.com>
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

microsoft/knowledge/testing/asserterror-needs-expectederror-and-code.md

@@ -0,0 +1,26 @@
+---
+bc-version: [all]
+domain: testing
+keywords: [asserterror, expectederror, expectederrorcode, negative-test, error-code]
+technologies: [al]
+countries: [w1]
+application-area: [all]
+---
+
+# Pin asserterror to a specific error with ExpectedError and ExpectedErrorCode
+
+## Description
+
+`asserterror` passes when the guarded statement raises any error at all. That is too permissive for a negative test: a typo, a missing setup record, or a permission failure all raise errors, so a bare `asserterror` can go green while never exercising the rule it claims to verify — false confidence that the validation works. Constrain it. `Assert.ExpectedError(text)` checks the message of the error that was actually raised, and `Assert.ExpectedErrorCode(code)` checks its error code. Together they assert that the specific failure occurred, turning "something went wrong" into "the right thing went wrong for the right reason".
+
+## Best Practice
+
+Follow every `asserterror` with a verification of the error it expects, and prefer the reusable `Library Assert` helpers over hardcoded literals. For a mandatory-field check, `Assert.ExpectedTestFieldError(FieldCaption, ExpectedValue)` encapsulates both the message and the `TestField` code, so the test survives caption or code changes and does not repeat that knowledge in every method. For other errors, pair `Assert.ExpectedError` with a stable substring — ideally a shared `Label`, not an inline sentence — and, where known, `Assert.ExpectedErrorCode`. When a needed check is missing from the shared library, extend `Library Assert` (or your own assert library) with a helper rather than hardcoding message text and codes across tests; matching on a code or an invariant fragment keeps the test from going blind to the wrong error when a caption is localized.
+
+See sample: `asserterror-needs-expectederror-and-code.good.al`.
+
+## Anti Pattern
+
+`asserterror DoInvalid();` with nothing after it. The test asserts only that the call failed somehow; swap the validation for a different bug and the test still passes, certifying a guard that may no longer fire. A negative test that cannot tell one error from another verifies almost nothing.
+
+See sample: `asserterror-needs-expectederror-and-code.bad.al`.