test: name the in-flight file and the native error when bun dies before its summary (#3037)

scripts/test-free-shards.ts

@@ -676,6 +676,8 @@ export interface FreeRunReport {
   inFlight: string[];
   /** Planned files never observed in the stream (silent passers + never-flushed wedges). */
   filesWithNoOutput: number;
+  /** The last nonblank line either stream printed: a native abort's message when bun dies without a summary. */
+  lastOutputLine: string | null;
 }
 
 interface FileProgress {
@@ -711,6 +713,7 @@ export class FreeRunReporter {
   private testsRan: number | null = null;
   private filesRan: number | null = null;
   private sawSummary = false;
+  private lastOutputLine: string | null = null;
 
   constructor(
     private readonly plannedFiles: string[],
@@ -758,6 +761,7 @@ export class FreeRunReporter {
       unhandledErrors: [...this.unhandled],
       inFlight,
       filesWithNoOutput: this.plannedFiles.filter((f) => !this.progress.has(normalizeRelativePath(f))).length,
+      lastOutputLine: this.lastOutputLine,
     };
   }
 
@@ -768,6 +772,7 @@ export class FreeRunReporter {
     // (fail) lines land under a second phantom file (observed on the first
     // Linux run: 5 real failures reported as 10 across 2 files).
     const line = stripAnsiLine(rawLine).replace(/^::group::/, '');
+    if (line.trim() !== '') this.lastOutputLine = line.trim();
     let visible = false;
     const failedCount = this.failureSummary.consume(line, origin);
     if (failedCount !== null) {
@@ -903,6 +908,10 @@ export function buildRunEpilogue(
   for (const u of report.unhandledErrors) {
     lines.push(`  ⚠ unhandled error between tests (around ${u.file ?? 'unknown file'})`);
   }
+  if (status === 'failed' && !report.sawTerminalSummary) {
+    lines.push(`  ⚠ test process ended before its summary; in flight: ${report.inFlight.length > 0 ? report.inFlight.join(', ') : 'unknown'}`);
+    if (report.lastOutputLine) lines.push(`  ⚠ last output: ${report.lastOutputLine}`);
+  }
   if (status === 'timed-out') {
     if (report.inFlight.length > 0) {
       lines.push(`  ⏱ in flight at kill: ${report.inFlight.join(', ')}`);

test/test-free-shards.test.ts

@@ -805,6 +805,17 @@ describe('test-free-shards: output contract (log capture, quiet console, failure
     expect(lines.some((l) => l.startsWith('[test:free] FAIL — '))).toBe(true);
   }, 30_000);
 
+  test('a test process that aborts before its summary names the in-flight file and its last output', () => {
+    const reporter = new FreeRunReporter(['test/done.test.ts', 'test/aborted.test.ts']);
+    reporter.write('::group::test/done.test.ts:\n(pass) fine\n::endgroup::\n', 'stdout');
+    reporter.write('::group::test/aborted.test.ts:\n(pass) first\n', 'stdout');
+    reporter.write('GetQueuedCompletionStatusEx: (735) ERROR_ABANDONED_WAIT_0\n', 'stderr');
+    reporter.end();
+    const lines = buildRunEpilogue('failed', reporter.report(), 16_000, '/tmp/x.log');
+    expect(lines).toContain('  ⚠ test process ended before its summary; in flight: test/aborted.test.ts');
+    expect(lines).toContain('  ⚠ last output: GetQueuedCompletionStatusEx: (735) ERROR_ABANDONED_WAIT_0');
+  });
+
   test('timeout with no observable header falls back to the buffered-parallel explanation', () => {
     const reporter = new FreeRunReporter(['test/a.test.ts', 'test/b.test.ts']);
     reporter.end();