Great question! I’ve spent a fair amount of time working with CTS-TradeFed, so let me walk you through exactly how it determines which modules and test cases to execute when you run run cts.

1. Device Profile Identification & Feature Matching #

First off, CTS-TradeFed starts by identifying the device’s type (phone, TV, wear, etc.) using system properties like ro.build.product and ro.product.device. Each device type has a predefined baseline of required modules tailored to its use case.

Next, it cross-references the device’s supported features—pulled from pm list features and the device’s system manifest—against each module’s dependencies. For example:

• Android TV devices don’t declare telephony-related features, so all CtsTelephony* modules get automatically skipped.
• TV-specific features like android.software.leanback trigger inclusion of modules like CtsLeanbackTestCases, which aren’t part of the phone’s default CTS run.

2. Module Configuration Rules #

Every CTS module has its own set of configuration rules (usually in the module’s AndroidManifest.xml or global CTS config files) that dictate eligibility:

• Minimum SDK version: Modules targeting API 30+ won’t run on devices with older Android versions.
• Hardware/software requirements: Annotations or manifest entries like <uses-feature android:name="android.hardware.camera"/> block the module if the device lacks that feature.
• Device type exclusions: Explicit tags like <exclude-if-device-type tv="true"/> in module configs prevent it from running on specific device categories.

When you run run cts, CTS-TradeFed parses all these configs and filters out any modules that don’t align with the target device’s specs.

3. Fine-Grained Test Case Filtering #

Even within an included module, not all test cases execute:

• Runtime feature checks: Test cases with annotations like @RequiresFeature("android.hardware.nfc") will skip themselves if the device doesn’t support that feature.
• Device-specific skips: Cases designed for touch-based interactions (common in phone tests) are often marked to skip on TV devices, which use remote controls instead.
• Disabled cases: Any test marked with @Disabled (either in code or via runtime config overrides) gets excluded from the run.

4. Optional Manual Overrides #

While the default run cts uses the device’s profile and feature set, you can tweak the module list with command-line flags:

• Use --include-module <module-name> to force-include a module that would otherwise be skipped.
• Use --exclude-module <module-name> to remove a module from the default run.
• Custom config files (in cts/config/) can also define global inclusion/exclusion rules that override the default behavior.

As a concrete example: When running CTS on an Android TV, you’ll notice far fewer telephony, camera, and touch-interaction modules compared to a phone. Instead, you’ll see extra modules focused on leanback UI, HDMI connectivity, and TV-specific media handling—all tied directly to the device’s declared features and profile.

内容的提问来源于stack exchange，提问作者Sanyal