Test Selection step

Works out which test units a change affects and writes the list for the test steps.

changed files ──► file rules ──► project graph ──► propagation ──► selection JSON
   env / git      full-run,       Xcode, SPM,        reverse deps     + per-ecosystem
                  ignore          Gradle, Flutter,   + test host       list files
                                  manual rules

How it decides

1. Changed files come from BITRISE_GIT_CHANGED_FILES. When the list is missing or marked incomplete, the step diffs HEAD against the merge base with base_ref, deepening the shallow clone the git-clone step leaves behind.
2. File rules run first. A file on the full-run list (lockfiles, xcconfig, root Gradle files, bitrise.yml, …) forces a full run. Ignored files (docs, markdown, GitHub metadata) are dropped.
3. The graph is built per ecosystem. Xcode: project.pbxproj build phases, synced folders, target dependencies, linked products, TEST_HOST, plus every local Swift package (Package.swift targets, products and .package(path:)). Gradle: an init script dumps projects, source sets and project dependencies. Flutter: pubspec.yaml path dependencies. Manual: glob => Test rules.
4. Ownership of each changed file: explicit membership, then globs, then the longest matching directory. A file nobody owns forces a full run (on_unknown_file).
5. Propagation follows reverse dependencies transitively, with no depth limit. A test unit is selected when it or anything it depends on changed, or when it matches a must-run pattern.

Any analysis error is a full run with the reason in the log and the JSON, never a guess.

Output

test-selection.json:

{
  "version": 1,
  "mode": "selected",
  "shadow": false,
  "reason": "3 changed files mapped onto the project graph",
  "changed_files": {"origin": "git", "complete": true, "base": "…", "count": 3, "files": ["…"]},
  "owners": [{"file": "Modules/Core/Sources/Cache.swift", "nodes": ["spm:Core/Core"]}],
  "affected_nodes": ["spm:Core/Core", "spm:Core/CoreTests", "xcode:App/App", "xcode:App/AppTests"],
  "tests": [
    {"id": "xcode:App/AppTests", "name": "AppTests", "ecosystem": "xcode", "selected": true,
     "reason": "via Core ← Modules/Core/Sources/Cache.swift", "identifiers": {"only_testing": "AppTests"}},
    {"id": "xcode:App/AppUITests", "name": "AppUITests", "ecosystem": "xcode", "selected": false,
     "reason": "no changed dependency", "identifiers": {"only_testing": "AppUITests"}}
  ],
  "stats": {"candidates": 2, "selected": 1, "skipped": 1, "must_run": 0}
}

Next to it, in selected mode only: xcode-only-testing.txt, gradle-modules.txt, flutter-packages.txt. In full mode no list file is written, because an empty list means "everything" to the consuming steps.

Trying it on a repository

export BITRISE_SOURCE_DIR=/path/to/repo
export changed_files="$(git -C $BITRISE_SOURCE_DIR diff --name-only origin/main...HEAD)"
export changed_files_complete=true
export project_path=App.xcworkspace scheme=App
export project_type=auto on_unknown_file=full mode=enforce on_error=full verbose=true
export repo_dir=$BITRISE_SOURCE_DIR output_dir=/tmp/test-selection
go run .

Or let the step diff itself: leave changed_files empty and set base_ref=main.

Development

go test ./...
go vet ./...