separate setting actions and reducers

test/background/reducers/setting.test.js

@@ -0,0 +1,19 @@
+import { expect } from "chai";
+import actions from 'background/actions';
+import settingReducer from 'background/reducers/setting';
+
+describe("setting reducer", () => {
+  it('return the initial state', () => {
+    let state = settingReducer(undefined, {});
+    expect(state).to.have.deep.property('value', {});
+  });
+
+  it('return next state for SETTING_SET_SETTINGS', () => {
+    let action = {
+      type: actions.SETTING_SET_SETTINGS,
+      value: { key: 123 },
+    };
+    let state = settingReducer(undefined, action);
+    expect(state).to.have.deep.property('value', { key: 123 });
+  });
+});