test(android): Stabilize InternalSentrySdk session persistence tests

[buenaflor]

📜 Description

Re-enable the ignored InternalSentrySdkTest for dropped unhandled errors. Make the fixture's executor configurable and opt into ImmediateExecutorService only in the three tests that read the persisted session. Other tests keep the default executor.

💡 Motivation and Context

The test added in #5990 was disabled in #6078 after intermittent FileNotFoundException failures. SDK initialization queues MovePreviousSession asynchronously; if it runs after the test persists its live session, it renames session.json to previous_session.json before the test reads it. Completing startup work synchronously in the affected tests removes that timing dependency.

💚 How did you test it?

• Ran :sentry-android-core:testReleaseUnitTest --tests='*InternalSentrySdkTest*' --rerun --no-daemon --no-configuration-cache on commit 13c17fac5700048893de0dd4af5f7e90e47c95d4 10 consecutive times, forcing fresh executions: all 24 tests passed in every run (240 test executions total), with zero failures, errors, or skips.
• spotlessApply apiDump: passed.
• During investigation, a deferred executor deterministically reproduced the missing-file exception by running queued startup work between the session write and read.

📝 Checklist

• I added GH Issue ID & Linear ID
• I added tests to verify the changes.
• No new PII added or SDK only sends newly added PII if sendDefaultPII is enabled.
• I updated the docs if needed.
• I updated the wizard if needed.
• Review from the native team if needed.
• No breaking change or entry added to the changelog.
• No breaking change for hybrid SDKs or communicated to hybrid SDKs.
• Public API changes reviewed by another Mobile SDK team member or implemented according to the develop docs spec.

🔮 Next steps

Follow up separately on the SDK's runtime ordering between startup session rotation and synchronous session persistence.

#skip-changelog

[sentry]

📲 Install Builds

Android

🔗 App Name	App ID	Version	Configuration
SDK Size	io.sentry.tests.size	8.55.0 (1)	release

⚙️ sentry-android Build Distribution Settings

[Copilot]

🟢 Approval recommended

The change is test-only and low risk, and the stabilization approach aligns with the described flake root cause.

Pull request overview

This PR stabilizes InternalSentrySdkTest session persistence behavior by making SDK startup/session-rotation work deterministic in the tests that read session.json, and re-enables the previously ignored flaky test.

Changes:

• Make the test fixture’s executor configurable so tests can force synchronous startup work when needed.
• Re-enable the previously @Ignored dropped-unhandled-error session persistence test by removing the timing dependency.
• Use ImmediateExecutorService only for the tests that read the persisted session file.

File summaries

File	Description
sentry-android-core/src/test/java/io/sentry/android/core/InternalSentrySdkTest.kt	Adds executor override to fixture init and applies ImmediateExecutorService to persisted-session-reading tests to prevent flaky FileNotFoundExceptions.

Review details

• Files reviewed: 1/1 changed files
• Comments generated: 1
• Review effort level: Lite

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