Add a unit test covering the trickier parts of the preview reducer

test/unit/redux/preview-test.js

+const tap = require('tap');
+const Preview = require('../../../src/redux/preview');
+const initialState = Preview.getInitialState();
+const reducer = Preview.previewReducer;
+
+let state;
+
+tap.tearDown(() => process.nextTick(process.exit));
+
+tap.test('Reducer', t => {
+    t.type(reducer, 'function');
+    t.type(initialState, 'object');
+
+    // Reducers should return their default state when called without state
+    let undefinedState;
+    t.deepEqual(initialState, reducer(undefinedState, {type: 'fake action'}));
+    t.end();
+});
+
+tap.test('resetProject', t => {
+    state = reducer({some: 'garbage'}, Preview.resetProject());
+    t.deepEqual(state, initialState);
+    t.end();
+});
+
+tap.test('setProjectInfo', t => {
+    // Initial values
+    t.equal(initialState.projectNotAvailable, false);
+    t.deepEqual(initialState.projectInfo, {});
+
+    // setProjectInfo action with an `info` value sets the projectInfo
+    state = reducer(initialState, Preview.setProjectInfo('a value'));
+    t.equal(state.projectInfo, 'a value');
+    t.equal(state.projectNotAvailable, false);
+
+    // setProjectInfo action with null info sets projectNotAvailable to true
+    // and resets the project info back to default state
+    state = reducer(initialState, Preview.setProjectInfo(null));
+    t.deepEqual(state.projectInfo, initialState.projectInfo);
+    t.equal(state.projectNotAvailable, true);
+    t.end();
+});
+
+tap.test('updateProjectInfo', t => {
+    const info = {a: 'value a', b: 'value b'};
+    state = reducer({projectInfo: info}, Preview.updateProjectInfo({
+        b: 'new value b',
+        c: 'new value c'
+    }));
+    t.deepEqual(state.projectInfo, {
+        a: 'value a',
+        b: 'new value b',
+        c: 'new value c'
+    });
+    t.end();
+});
+
+tap.test('setComments', t => {
+    // Initial value
+    t.deepEqual(initialState.comments, []);
+
+    state = reducer(initialState, Preview.setComments([1, 2]));
+    state = reducer(state, Preview.setComments([3, 4]));
+    t.deepEqual(state.comments, [1, 2, 3, 4]);
+
+    t.end();
+});
+
+const commentState = {
+    comments: [
+        {id: 'id1', visibility: 'visible'},
+        {id: 'id2', visibility: 'visible'},
+        {id: 'id3', visibility: 'visible'}
+    ],
+    replies: {
+        id1: [
+            {id: 'id4', visibility: 'visible'},
+            {id: 'id5', visibility: 'visible'}
+        ]
+    }
+};
+
+tap.test('setCommentDeleted, top level comment', t => {
+    state = reducer(commentState, Preview.setCommentDeleted('id2'));
+    t.equal(state.comments[1].visibility, 'deleted');
+    t.end();
+});
+
+tap.test('setCommentDeleted, reply comment', t => {
+    state = reducer(commentState, Preview.setCommentDeleted('id4', 'id1'));
+    t.equal(state.replies.id1[0].visibility, 'deleted');
+    t.end();
+});
+
+tap.test('setRepliesDeleted/Restored', t => {
+    state = reducer(commentState, Preview.setRepliesDeleted('id1'));
+    t.equal(state.replies.id1[0].visibility, 'deleted');
+    t.equal(state.replies.id1[1].visibility, 'deleted');
+
+    state = reducer(state, Preview.setRepliesRestored('id1'));
+    t.equal(state.replies.id1[0].visibility, 'visible');
+    t.equal(state.replies.id1[1].visibility, 'visible');
+    t.end();
+});
+
+tap.test('setCommentReported, top level comment', t => {
+    state = reducer(commentState, Preview.setCommentReported('id2'));
+    t.equal(state.comments[1].visibility, 'reported');
+    t.end();
+});
+
+tap.test('setCommentReported, reply comment', t => {
+    state = reducer(commentState, Preview.setCommentReported('id4', 'id1'));
+    t.equal(state.replies.id1[0].visibility, 'reported');
+    t.end();
+});
+
+tap.test('addNewComment, top level comment', t => {
+    state = reducer(commentState, Preview.addNewComment({id: 'new comment'}));
+    // Adds comment to beginning of list
+    t.equal(state.comments[0].id, 'new comment');
+    t.end();
+});
+
+tap.test('addNewComment, reply comment', t => {
+    state = reducer(commentState, Preview.addNewComment({id: 'new comment'}, 'id1'));
+    // Adds replies to the end of the replies list
+    t.equal(state.replies.id1[2].id, 'new comment');
+    t.end();
+});