Conversation
Add compatibility tests for the $lastN accumulator, covering both success and error behavior: - test_accumulator_lastN.py: n vs group size, sort-order dependence, null/missing handling (included, not skipped), mixed BSON types, and empty groups. - test_accumulator_lastN_errors.py: missing, zero, negative, and non-integer n. Missing n fails with N_ACCUMULATOR_MISSING_N_FIRSTN_FAMILY_ERROR (5787906); any other invalid n fails with N_ACCUMULATOR_INVALID_N_ERROR (7548606), matching the existing $group N-accumulator error tests. Signed-off-by: Sunita Bhattacharya <sunitab55@gmail.com>
sbhattap
changed the title
There was a problem hiding this comment.
Pull request overview
Adds a full compatibility test suite for the $lastN accumulator under the existing accumulator test hierarchy, expanding coverage beyond the existing smoke test to include both success and validation-error behaviors.
Changes:
- Added a parametrized
$lastNsuccess suite covering group-size boundaries, sort-order dependence, null/missing inclusion semantics, mixed-type preservation, and empty-collection behavior. - Added a parametrized
$lastNerror suite covering missingnand invalidnvalues with assertions against established error-code constants. - Added an (empty)
__init__.pyto align thelastN/directory with other accumulator test package layouts.
Reviewed changes
Copilot reviewed 2 out of 3 changed files in this pull request and generated 3 comments.
| File | Description |
|---|---|
| documentdb_tests/compatibility/tests/core/operator/accumulators/lastN/test_accumulator_lastN.py | New parametrized $lastN success-behavior coverage across ordering, boundaries, and type/null semantics. |
| documentdb_tests/compatibility/tests/core/operator/accumulators/lastN/test_accumulator_lastN_errors.py | New parametrized $lastN negative tests asserting correct error codes for invalid/missing n. |
| documentdb_tests/compatibility/tests/core/operator/accumulators/lastN/init.py | Adds package marker file for directory consistency with other accumulator suites. |
Comment on lines
+73
to
+88
| AccumulatorTestCase( | ||
| "n_as_long", | ||
| docs=[{"_id": 0, "v": 10}, {"_id": 1, "v": 20}, {"_id": 2, "v": 30}], | ||
| pipeline=[ | ||
| {"$sort": {"_id": 1}}, | ||
| { | ||
| "$group": { | ||
| "_id": None, | ||
| "result": {"$lastN": {"n": {"$toLong": 2}, "input": "$v"}}, | ||
| } | ||
| }, | ||
| {"$project": {"_id": 0, "result": 1}}, | ||
| ], | ||
| expected=[{"result": [20, 30]}], | ||
| msg="$lastN should accept a long-typed n value", | ||
| ), |
Comment on lines
+11
to
+12
| import pytest | ||
| from bson import Decimal128 |
sbhattap
marked this pull request as draft
July 12, 2026 18:34
documentdb-triage-tool
Bot
added
compatibility test
|
🤖 Auto-triaged by documentdb-triage-tool. Applied: Reasoningcomponent from path globs (test-coverage); effort from diff stats (391+0 LOC, 3 files); LLM: Adds new compatibility test files for the $lastN accumulator under the test-coverage paths, expanding coverage with no functional or schema changes. If a label is wrong, remove it manually and ping |
Signed-off-by: Sunita Bhattacharya <sunitab55@gmail.com>
test_accumulator_lastN_errors.py: add error cases for malformed specification, missing input, and non-coercible n. test_accumulator_lastN.py: add behavior cases for per-group accumulation and filtered-to-empty groups. Signed-off-by: Sunita Bhattacharya <sunitab55@gmail.com>
test_expression_lastN.py: cover n-vs-length, n typing, element preservation, field references, and invalid n / input handling. Includes the non-coercible n path (NaN, infinity, overflow), where the expression and accumulator forms report the same code. Signed-off-by: Sunita Bhattacharya <sunitab55@gmail.com>
sbhattap
changed the title
sbhattap
changed the title
sbhattap
marked this pull request as ready for review
September 30, 2026 04:18
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
PR Description:
Summary
$lastNin both of its forms: the$groupaccumulator and the arrayexpression used inside
$projectCovers tests for #473 (accumulator form) and #199 (array-expression form).
Test Coverage
$lastNhas two independent implementations that behave differently, so each is covered separately:accumulators/lastN/test_accumulator_lastN.pyaccumulators/lastN/test_accumulator_lastN_errors.pynandinput, non-positive and non-integern, non-coerciblenexpressions/array/lastN/test_expression_lastN.pyntyping (int/long/double/expression), element preservation without traversal,nandinputas field paths, invalidnand non-arrayinputframework/error_codes.py$lastNspec,n, andinputvalidation (5787801, 5787901, 5787902, 5787903, 5787907, 5787908, 5788200)Key behavioral differences tested:
or non-array
inputoutright (5788200)ncollapses to a single generic code (7548606) in the accumulator, but reports granularcodes (
5787902/5787903/5787908) in the expression40237in the accumulator and5787801in the expression, foridentical input
n= NaN, infinity, or an out-of-range double reports31109in both forms — the oneinvalid-
npath where they agreeTest plan
Type of Change
AI Disclosure
Checklist
git commit -s)