docs(agents): Prefer Google Truth for new unit test assertions

[runningcode]

📜 Description

Adds guidance for AI coding agents to prefer Google Truth (com.google.common.truth.Truth.assertThat) over kotlin.test/JUnit assertions when writing assertions in new unit tests, while continuing to use kotlin.test for test structure (@Test, assertFailsWith).

Updated files:

• AGENTS.md — two bullets under Testing Requirements covering the preference, a pointer to sentry/src/test/java/io/sentry/DsnTest.kt as the reference style, and the per-module testImplementation(libs.google.truth) requirement.
• .cursor/rules/coding.mdc — a concise version of the same guidance (this rule is alwaysApply: true).

💡 Motivation and Context

Truth (v1.4.5) is already a dependency in the sentry module and used in DsnTest.kt, but the rest of the repo uses kotlin.test. This documents Truth as the preferred choice going forward so new tests get its more readable, fluent assertions. The guidance explicitly avoids churn by not rewriting existing assertions solely to switch libraries.

💚 How did you test it?

Documentation-only change to agent instruction files. Ran ./gradlew spotlessApply apiDump with no resulting code changes.

📝 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.

🔮 Next steps

As modules gain Truth-based tests, add testImplementation(libs.google.truth) to their build.gradle.kts.

#skip-changelog

[sentry]

📲 Install Builds

Android

🔗 App Name	App ID	Version	Configuration
SDK Size	io.sentry.tests.size	8.47.0 (1)	release

⚙️ sentry-android Build Distribution Settings