test(mfa): pin the INIT executor to the single test scenario

Recovering the scenario from the step event existed for the era of two
INIT fixtures, which ended when the unobserved payload variant was
dropped. With one fixture the recovery added a type guard, an
impossible throw, and a step-typed executor signature without carrying
any information, so the executor now starts MFA_TEST_SCENARIO_NAME
directly and every executor is a plain thunk.

Author: dariusz-biela

tests/unit/components/MultifactorAuthentication/machine/graphTraversal/viewMatchesMachine.test.tsx

@@ -1,5 +1,5 @@
 import {act, fireEvent, screen} from '@testing-library/react-native';
-import {isTestScenarioInitEvent} from 'tests/utils/mfa/flowFixtures';
+import {MFA_TEST_SCENARIO_NAME} from 'tests/utils/mfa/flowFixtures';
 import getWalkedPaths from 'tests/utils/mfa/flowPaths';
 import {getMfaControls, renderMfaUi} from 'tests/utils/mfa/realUi/harness';
 import {pendingModalClose, resetMfaUiMocks} from 'tests/utils/mfa/realUi/mocks';
@@ -45,25 +45,18 @@ const MFA_STATE = CONST.MULTIFACTOR_AUTHENTICATION.MFA_STATE;
 
 type MfaEventType = MfaEvent['type'];
 
-/**
- * The event carries only its `type` here because `xstate/graph` erases the remaining fields from the
- * executor's step type. The INIT executor recovers them through `isTestScenarioInitEvent`.
- */
-type MfaEventExecutor = (step: {event: {type: MfaEventType}}) => Promise<void>;
+type MfaEventExecutor = () => Promise<void>;
 
 /**
- * `INIT` starts a flow through the public API, using the scenario from the step's own event.
- * `MODAL_CLOSED` runs the navigator's teardown callback. `satisfies Record<MfaEventType, ...>`
- * requires an explicit executor for every machine event.
+ * Maps every machine event to the action that produces it in the rendered app, such as a button press
+ * or a navigator callback. The walk drives each path step through this table, and the `satisfies`
+ * clause makes a machine event without an executor fail compilation.
  */
 /* eslint-disable @typescript-eslint/naming-convention -- keys mirror the machine's event type union. */
 const mfaEventExecutors = {
-    INIT: async ({event}) => {
-        if (!isTestScenarioInitEvent(event)) {
-            throw new Error(`The INIT executor received an event outside the test-scenario fixtures: ${JSON.stringify(event)}`);
-        }
+    INIT: async () => {
         await act(async () => {
-            await getMfaControls().executeScenario(event.scenarioName);
+            await getMfaControls().executeScenario(MFA_TEST_SCENARIO_NAME);
         });
         await waitForBatchedUpdatesWithAct();
         // The initial screen's `onLayout` does not fire in jsdom, so the test calls the same handler to flush the

tests/utils/mfa/flowFixtures.ts

@@ -16,15 +16,5 @@ function createInitEvent(): MultifactorAuthenticationInitEvent<typeof MFA_TEST_S
     };
 }
 
-/**
- * Narrows a traversal event to the test-scenario INIT fixture shape. The scenario-name check is enough,
- * because {@link createInitEvent} is the only place that builds INIT events for the traversal. The
- * parameter accepts any typed event, because `xstate/graph` erases everything but `type` from the
- * event an executor receives.
- */
-function isTestScenarioInitEvent(event: {type: string}): event is MultifactorAuthenticationInitEvent<typeof MFA_TEST_SCENARIO_NAME> {
-    return event.type === 'INIT' && 'scenarioName' in event && event.scenarioName === MFA_TEST_SCENARIO_NAME;
-}
-
 export default createInitEvent;
-export {isTestScenarioInitEvent, MFA_TEST_SCENARIO_NAME};
+export {MFA_TEST_SCENARIO_NAME};