add tests for firmware reducers

src/firmware/reducers.test.ts

@@ -0,0 +1,39 @@
+// SPDX-License-Identifier: MIT
+// Copyright (c) 2021 The Pybricks Authors
+
+import { Action } from '../actions';
+import {
+    FailToFinishReasonType,
+    didFailToFinish,
+    didFinish,
+    didProgress,
+    didStart,
+} from './actions';
+import reducers from './reducers';
+
+type State = ReturnType<typeof reducers>;
+
+test('initial state', () => {
+    expect(reducers(undefined, {} as Action)).toMatchInlineSnapshot(`
+        Object {
+          "flashing": false,
+          "progress": null,
+        }
+    `);
+});
+
+test('flashing', () => {
+    expect(reducers({ flashing: false } as State, didStart()).flashing).toBe(true);
+    expect(reducers({ flashing: true } as State, didFinish()).flashing).toBe(false);
+    expect(
+        reducers(
+            { flashing: true } as State,
+            didFailToFinish(FailToFinishReasonType.TimedOut),
+        ).flashing,
+    ).toBe(false);
+});
+
+test('progress', () => {
+    expect(reducers({ progress: 1 } as State, didStart()).progress).toBe(null);
+    expect(reducers({ progress: null } as State, didProgress(1)).progress).toBe(1);
+});