[trask]

Add InMemoryMetricExporter.builder() with a temporality selector so tests can select temporality by instrument type without a custom exporter wrapper.

InMemoryMetricExporter exporter =
    InMemoryMetricExporter.builder()
        .setAggregationTemporalitySelector(AggregationTemporalitySelector.deltaPreferred())
        .build();

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.

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

[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.

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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 90.37%. Comparing base (1acb73a) to head (38e1cec).

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #8993      +/-   ##
============================================
- Coverage     90.37%   90.37%   -0.01%     
- Complexity    11012    11016       +4     
============================================
  Files          1020     1021       +1     
  Lines         30119    30127       +8     
  Branches       3932     3932              
============================================
+ Hits          27219    27226       +7     
  Misses         1941     1941              
- Partials        959      960       +1     

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[jack-berg]

InMemoryMetricReader started with just create() methods, but expanded to a builder because the configuration footprint expanded to include setAggregationTemporalitySelector, setDefaultAggregationSelector, setMemoryMode. I see InMemoryMetricExporter going the same way so let's just jump to the builder now anticipating the setMemoryMode and setDefaultAggregationSeletor configuration options.