test: Set up flattening benchmarks

[edgarrmondragon]

SSIA

Summary by Sourcery

Tests:

• Introduce pytest benchmark suite for flatten_key, flatten_record, and flatten_schema under varying record and schema shapes.

[sourcery-ai]

Reviewer's Guide

Adds pytest-based benchmark tests that exercise singer_sdk.helpers._flattening functions (flatten_key, flatten_record, flatten_schema) across short/long key inputs and wide/deep record and schema structures to measure performance characteristics under different shapes and depths of data.

File-Level Changes

Change	Details	Files
Introduce pytest benchmark suite for flatten_key, flatten_record, and flatten_schema under varied key, record, and schema shapes.	Add fixtures to generate short and long key inputs for flatten_key benchmarks. Add fixtures to generate wide flat records/schemas and deeply nested records/schemas for flatten_record and flatten_schema benchmarks. Implement benchmark tests for flatten_key with short and long keys using the pytest benchmark fixture. Implement benchmark tests for flatten_record using pre-flattened schemas for wide and deeply nested data structures. Implement benchmark tests for flatten_schema over wide and deeply nested schemas with controlled max_level parameters.	tests/benchmarks/test_flattening.py

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 94.21%. Comparing base (1053b7b) to head (be9c26d).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3686   +/-   ##
=======================================
  Coverage   94.21%   94.21%           
=======================================
  Files          73       73           
  Lines        6208     6208           
  Branches      763      763           
=======================================
  Hits         5849     5849           
  Misses        267      267           
  Partials       92       92           

Flag	Coverage Δ
core	83.05% <ø> (ø)
end-to-end	76.03% <ø> (ø)
optional-components	44.86% <ø> (ø)

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[codspeed-hq]

Merging this PR will not alter performance

✅ 8 untouched benchmarks
🆕 6 new benchmarks

Performance Changes

	Benchmark	BASE	HEAD	Efficiency
🆕	test_bench_flatten_key_long	N/A	136.1 µs	N/A
🆕	test_bench_flatten_key_short	N/A	35.5 µs	N/A
🆕	test_bench_flatten_record_deep	N/A	3.2 ms	N/A
🆕	test_bench_flatten_record_wide	N/A	357.9 µs	N/A
🆕	test_bench_flatten_schema_deep	N/A	4.5 ms	N/A
🆕	test_bench_flatten_schema_wide	N/A	1 ms	N/A

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_{Comparing test/flattenning-benchamarks (be9c26d) with main (1053b7b)}

[edgarrmondragon]

@sourcery-ai review

[sourcery-ai]

Hey - I've found 1 issue

Prompt for AI Agents

Please address the comments from this code review:

## Individual Comments

### Comment 1
<location path="tests/benchmarks/test_flattening.py" line_range="15" />
<code_context>
+    flatten_schema,
+)
+
+NUMBER_OF_RUNS = 250
+
+
</code_context>
<issue_to_address>
**suggestion (testing):** Manual inner loop over `NUMBER_OF_RUNS` may fight against pytest-benchmark’s own timing controls

Wrapping each benchmarked call in a `run()` that loops `NUMBER_OF_RUNS` times duplicates pytest-benchmark’s own iteration control and can distort or obscure the timing results. Instead, pass the operation directly to `benchmark` (e.g. `benchmark(flatten_key, key, parents)` or `benchmark.pedantic(...)`) and, if needed, adjust the number of rounds via the fixture configuration rather than a custom loop.

Suggested implementation:

```python
from singer_sdk.helpers._flattening import (
    flatten_key,
    flatten_record,
    flatten_schema,
)

from __future__ import annotations

import itertools

import pytest

from singer_sdk.helpers._flattening import (
    flatten_key,
    flatten_record,
    flatten_schema,

```

```python

```

```python
def test_flatten_key_benchmark(benchmark, key, parents):
    benchmark(flatten_key, key, parents)

```

```python
def test_flatten_record_benchmark(benchmark, record, schema):
    benchmark(flatten_record, record, schema)

```

```python
def test_flatten_schema_benchmark(benchmark, schema):
    benchmark(flatten_schema, schema)

```

If you want multiple rounds or warmup behavior, configure this via pytest-benchmark instead of a manual loop, e.g.:
- In `pytest.ini` or `pyproject.toml`, set options such as `benchmark_min_rounds`, `benchmark_max_time`, `benchmark_warmup` as needed.
- Alternatively, if you need more control per-test, you can use `benchmark.pedantic(flatten_key, args=(key, parents), iterations=1, rounds=250)` instead of the simple `benchmark(...)` call, which still avoids a custom inner loop while keeping iteration control with pytest-benchmark.
</issue_to_address>

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[sourcery-ai]

Hey - I've reviewed your changes and they look great!

---

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