Add abs expression tests

[danielfrankcom]

This change adds tests for the abs expression. It was originally authored by @vic-tsang.

Closes #272

[documentdb-triage-tool]

🤖 Auto-triaged by documentdb-triage-tool.

Applied: compatibility test, enhancement
Project fields suggested: Component test-coverage · Priority P2 · Effort L · Status Needs Review
Confidence: 0.30 (deterministic)

Reasoning

component from path globs (test-coverage); effort from diff stats (724+0 LOC, 7 files); LLM failed: Invalid response body while trying to fetch https://api.anthropic.com/v1/messages: Premature close

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[PatersonProjects]

I think we should probably add in docStrings for these files

[danielfrankcom]

I think we should probably add in docStrings for these files

Assuming you mean module docstrings here, since there are already docstrings for the property groups. Just pushed a change with those, please let me know if you meant something else.

[PatersonProjects]

I think we should probably add in docStrings for these files

Assuming you mean module docstrings here, since there are already docstrings for the property groups. Just pushed a change with those, please let me know if you meant something else.

That is what I meant! Sorry should've been clearer

[PatersonProjects]

It looks good to me, but you may want to consider adding a nested field path test?
{"a": [{"b": -1}, {"b": -2}]}, expression {"$abs": "$a.b"}

[ramgokul-14]

Are tests in other contexts per https://github.com/documentdb/functional-tests/blob/main/docs/testing/TEST_COVERAGE.md#11-expression-operator-in-pipeline-contexts in scope for this change?

[danielfrankcom]

Are tests in other contexts per https://github.com/documentdb/functional-tests/blob/main/docs/testing/TEST_COVERAGE.md#11-expression-operator-in-pipeline-contexts in scope for this change?

I think this is out of scope for expression-level changes, it falls within the scope of integration tests for the consuming aspects, like stages/project/test_project_expressions.py for example.