Add a test to check Ctrl+C interruption during the VU init phase

As I've mentioned in the code comments, this test doesn't test the eventually desired behavior, it tests the currently expected behavior as it is. The current behavior is still much better than the behavior before this PR, where the VU init was interrupted without any handling and graceful stops. However, the fix to actually abort k6 with the correct exit code and run_status will be in another PR.

cmd/integration_test.go

@@ -1068,6 +1068,45 @@ func testAbortedByScriptTestAbort(
 	return ts
 }
 
+func TestAbortedByInterruptDuringVUInit(t *testing.T) {
+	t.Parallel()
+	script := []byte(`
+		import { sleep } from 'k6';
+		export const options = {
+			vus: 5,
+			duration: '10s',
+		};
+
+		if (__VU > 1) {
+			console.log('VU init sleeping for a while');
+			sleep(100);
+		}
+
+		export default function () {};
+	`)
+
+	// TODO: fix this to exect lib.RunStatusAbortedUser and
+	// exitcodes.ExternalAbort
+	//
+	// This is testing the current behavior, which is expected, but it's not
+	// actually the desired one! See https://github.com/grafana/k6/issues/2804
+	ts := getSimpleCloudOutputTestState(
+		t, script, nil, lib.RunStatusAbortedSystem, cloudapi.ResultStatusPassed, int(exitcodes.GenericEngine),
+	)
+	asyncWaitForStdoutAndStopTestWithInterruptSignal(t, ts, 15, time.Second, "VU init sleeping for a while")
+	newRootCommand(ts.globalState).execute()
+
+	stdOut := ts.stdOut.String()
+	t.Log(stdOut)
+
+	assert.Contains(t, stdOut, `level=debug msg="Stopping k6 in response to signal..." sig=interrupt`)
+	assert.Contains(t, stdOut, `level=debug msg="Metrics emission of VUs and VUsMax metrics stopped"`)
+
+	// TODO: same as above, fix expected error message and run_status to 5
+	assert.Contains(t, stdOut, `level=debug msg="Sending test finished" output=cloud ref=111 run_status=6 tainted=false`)
+	assert.Contains(t, stdOut, `level=error msg="context canceled`)
+}
+
 func TestAbortedByScriptInitError(t *testing.T) {
 	t.Parallel()
 	script := []byte(`