Add tests for reducer utility functions

h/static/scripts/reducers/test/util-test.js

+'use strict';
+
+var util = require('../util');
+
+var fixtures = {
+  update: {
+    ADD_ANNOTATIONS: function (state, action) {
+      if (!state.annotations) {
+        return {annotations: action.annotations};
+      }
+      return {annotations: state.annotations.concat(action.annotations)};
+    },
+    SELECT_TAB: function (state, action) {
+      return {tab: action.tab};
+    },
+  },
+  countAnnotations: function (state) {
+    return state.annotations.length;
+  },
+};
+
+describe('reducer utils', function () {
+  describe('#actionTypes', function () {
+    it('returns an object with values equal to keys', function () {
+      assert.deepEqual(util.actionTypes({
+        SOME_ACTION: sinon.stub(),
+        ANOTHER_ACTION: sinon.stub(),
+      }), {
+        SOME_ACTION: 'SOME_ACTION',
+        ANOTHER_ACTION: 'ANOTHER_ACTION',
+      });
+    });
+  });
+
+  describe('#createReducer', function () {
+    it('returns a reducer that combines each update function from the input object', function () {
+      var reducer = util.createReducer(fixtures.update);
+      var newState = reducer({}, {
+        type: 'ADD_ANNOTATIONS',
+        annotations: [{id: 1}],
+      });
+      assert.deepEqual(newState, {
+        annotations: [{id: 1}],
+      });
+    });
+
+    it('returns a new object if the action was handled', function () {
+      var reducer = util.createReducer(fixtures.update);
+      var originalState = {someFlag: false};
+      assert.notEqual(reducer(originalState, {type: 'SELECT_TAB', tab: 'notes'}),
+        originalState);
+    });
+
+    it('returns the original object if the action was not handled', function () {
+      var reducer = util.createReducer(fixtures.update);
+      var originalState = {someFlag: false};
+      assert.equal(reducer(originalState, {type: 'UNKNOWN_ACTION'}), originalState);
+    });
+
+    it('preserves state not modified by the update function', function () {
+      var reducer = util.createReducer(fixtures.update);
+      var newState = reducer({otherFlag: false}, {
+        type: 'ADD_ANNOTATIONS',
+        annotations: [{id: 1}],
+      });
+      assert.deepEqual(newState, {
+        otherFlag: false,
+        annotations: [{id: 1}],
+      });
+    });
+  });
+
+  describe('#bindSelectors', function () {
+    it('bound functions call original functions with current value of getState()', function () {
+      var annotations = [{id: 1}];
+      var getState = sinon.stub().returns({annotations: annotations});
+      var bound = util.bindSelectors({
+        countAnnotations: fixtures.countAnnotations,
+      }, getState);
+
+      assert.equal(bound.countAnnotations(), 1);
+
+      getState.returns({annotations: annotations.concat([{id: 2}])});
+      assert.equal(bound.countAnnotations(), 2);
+    });
+  });
+});