KMP-IMPACT

Phase 3 — Dynamic analysis (DroidBot)

The third phase compares the UI navigation graph of the BEFORE and AFTER APKs. It detects screens that exist in only one state and edges that appear or disappear, labelling them as regression, addition, or no-change.

Inputs

phase1/before/, phase1/after/ — shadow copies from Phase 1.
A running Android emulator (locally or via reactivecircus/android-emulator-runner in CI).

Outputs

phase3/
├── before.utg/             # DroidBot UTG, BEFORE APK
├── after.utg/              # DroidBot UTG, AFTER APK
└── ui_regressions.json

What happens

Assemble the debug APK on the BEFORE shadow copy with ./gradlew :<android-module>:assembleDebug. If this fails, mark Phase 3 BLOCKED — APK assembly failed (BEFORE) and stop.
Same for AFTER.
Install the BEFORE APK on the emulator. Run DroidBot for the configured budget — defaults count = 100, timeout = 90, policy = dfs_greedy, -grant_perm, -is_emulator. Persist the UTG to phase3/before.utg/.
Uninstall the BEFORE APK, install AFTER. Repeat DroidBot. Persist to phase3/after.utg/.
Diff the two UTGs at the state level. State identity is based on the activity name plus the set of clickable element IDs — DroidBot’s default heuristic.

Output sample

{
  "status": "completed",
  "blocked_reason": "",
  "before_screens": ["MainActivity", "DetailActivity"],
  "after_screens":  ["MainActivity", "DetailActivity"],
  "diffs": [],
  "activity_coverage_before": { "MainActivity": 18, "DetailActivity": 6 },
  "activity_coverage_after":  { "MainActivity": 17, "DetailActivity": 7 },
  "nodes_before": 14, "nodes_after": 14,
  "structures_before": 6, "structures_after": 6
}

On failure the same model carries a blocked status and an empty payload:

{
  "status": "blocked",
  "blocked_reason": "DroidBot produced no UTG artifact",
  "before_screens": [],
  "after_screens": [],
  "diffs": []
}

Edge cases

Build failure on BEFORE or AFTER. Most common cause is Kotlin 2.x without the Compose Compiler plugin. See L4.
Android module not detected. The workflow probes the module names listed in Reference → GitHub Action. If none match, expose your real module under one of those aliases.
Empty UTG. The merge step rejects empty UTG folders on purpose — an empty artifact would mask a real failure.
Emulator unavailable. Locally, fall back to --skip-dynamic. In CI, the emulator is provided by reactivecircus/android-emulator-runner.

Contracts

Next phase

Phase 4 reads phase2/impact_graph.json and phase3/ui_regressions.json and produces the canonical consolidated.json.

→ Phase 4 — Consolidation

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