[trask]

Related to open-telemetry/opentelemetry-java-instrumentation#21111

Allow InMemoryMetricExporter to accept an AggregationTemporalitySelector, so tests can select temporality by instrument type without a custom exporter wrapper.

InMemoryMetricExporter exporter =
    InMemoryMetricExporter.create(AggregationTemporalitySelector.deltaPreferred());

This uses delta temporality for counters and histograms while keeping up-down counters cumulative.

Existing factories retain their behavior: create() uses cumulative temporality for all instruments, and create(AggregationTemporality) applies the given temporality to every instrument type.

[otelbot]

⚠️ API changes detected — additional maintainer review required

@jack-berg @jkwatson

This PR modifies the public API surface area of the following module(s):

• opentelemetry-sdk-testing

Please review the changes in docs/apidiffs/current_vs_latest/ carefully before approving.

[opentelemetry-pr-dashboard]

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[Copilot]

🟢 Approval recommended

No active review issues block the temporality-selector factory change.

No open issues 🎉

What changed in this PR

Adds instrument-specific temporality selection to InMemoryMetricExporter, allowing tests to use selectors such as deltaPreferred() without a custom exporter wrapper.

Changes:

• Adds a selector-based factory while preserving the behavior of existing factories.
• Expands tests for temporality selection, null-selector rejection, metric collection, and exported-data preservation.
• Updates the API compatibility report to record the new overload.

File	Description
sdk/​testing/​src/​test/​java/​io/​opentelemetry/​sdk/​testing/​exporter/​InMemoryMetricExporterTest.java	Tests selector behavior and preserves coverage of existing factories.
sdk/​testing/​src/​main/​java/​io/​opentelemetry/​sdk/​testing/​exporter/​InMemoryMetricExporter.java	Adds the selector factory and delegates temporality selection to it.
docs/​apidiffs/​current_vs_latest/​opentelemetry-sdk-testing.txt	Records the new public factory overload.

_{Review effort: Balanced}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.38%. Comparing base (dc3019e) to head (4884813).

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #8993      +/-   ##
============================================
+ Coverage     90.36%   90.38%   +0.01%     
- Complexity    10995    10996       +1     
============================================
  Files          1020     1020              
  Lines         30096    30098       +2     
  Branches       3929     3929              
============================================
+ Hits          27197    27203       +6     
+ Misses         1942     1937       -5     
- Partials        957      958       +1     

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