trying all sorts of different layout strategies

src/commands/Commands.test.js

       startApp: jest.fn()
     };
     require('react-native').NativeModules.NativeNavigation = mockNativeNavigation;
-    jest.mock('../providers/UniqueIdProvider');
     uut = require('./Commands');
   });
 

src/commands/LayoutBuilder.js

 import {uniqueId} from '../providers/UniqueIdProvider';
 
 export function parse(params) {
-  const layout = _.assign({}, params);
+  const layout = _.merge({}, params);
   if (layout.container) {
     layout.container.id = uniqueId(`container`);
   }
       layout.sideMenu.right.id = uniqueId(`container`);
     }
   }
+  if (layout.tabs) {
+    _.forEach(layout.tabs, (t) => t.container.id = uniqueId(`container`));
+  }
   return layout;
 }

src/commands/LayoutBuilder.test.js

 describe('LayoutBuilder', () => {
-  let uut;
+  let LayoutBuilder;
 
   beforeEach(() => {
     jest.mock('../providers/UniqueIdProvider');
-    uut = require('./LayoutBuilder');
+    LayoutBuilder = require('./LayoutBuilder');
   });
 
   describe('parse', () => {
-    it('returns a new object', () => {
-      const input = {};
-      expect(uut.parse(input)).not.toBe(input);
+    it('deeply clones input params', () => {
+      const input = {inner: {value: 1}};
+      expect(LayoutBuilder.parse(input)).not.toBe(input);
+      expect(LayoutBuilder.parse(input).inner).not.toBe(input.inner);
+    });
+
+    it('adds uniqueId to passed container', () => {
+      expect(LayoutBuilder.parse({
+        container: {
+          key: 'com.example.MyScreen'
+        }
+      })).toEqual({
+        container: {
+          key: 'com.example.MyScreen',
+          id: 'containerUNIQUE'
+        }
+      });
     });
 
     it('adds uniqueId to passed sideMenu', () => {
-      expect(uut.parse({
+      expect(LayoutBuilder.parse({
         container: {
           key: 'com.example.MyScreen'
         },
       })).toEqual({
         container: {
           key: 'com.example.MyScreen',
-          id: 'container123'
+          id: 'containerUNIQUE'
         },
         sideMenu: {
           left: {
             key: 'com.example.SideMenu1',
-            id: 'container123'
+            id: 'containerUNIQUE'
           },
           right: {
             key: 'com.example.SideMenu2',
-            id: 'container123'
+            id: 'containerUNIQUE'
           }
         }
       });
     });
 
-    it('adds uniqueId to passed container', () => {
-      expect(uut.parse({
-        container: {
-          key: 'com.example.MyScreen'
+    it('adds uniqueId to passed tabs', () => {
+      expect(LayoutBuilder.parse({
+        tabs: [
+          {
+            container: {
+              key: 'com.example.FirstTab'
+            }
+          },
+          {
+            container: {
+              key: 'com.example.SecondTab'
+            }
+          },
+          {
+            container: {
+              key: 'com.example.FirstTab'
+            }
+          }
+        ],
+        sideMenu: {
+          left: {
+            key: 'com.example.Menu1'
+          },
+          right: {
+            key: 'com.example.Menu2'
+          }
         }
       })).toEqual({
-        container: {
-          key: 'com.example.MyScreen',
-          id: 'container123'
+        tabs: [
+          {
+            container: {
+              key: 'com.example.FirstTab',
+              id: 'containerUNIQUE'
+            }
+          },
+          {
+            container: {
+              key: 'com.example.SecondTab',
+              id: 'containerUNIQUE'
+            }
+          },
+          {
+            container: {
+              key: 'com.example.FirstTab',
+              id: 'containerUNIQUE'
+            }
+          }
+        ],
+        sideMenu: {
+          left: {
+            key: 'com.example.Menu1',
+            id: 'containerUNIQUE'
+          },
+          right: {
+            key: 'com.example.Menu2',
+            id: 'containerUNIQUE'
+          }
         }
       });
     });

src/commands/ValidCommands.test.js → src/commands/ValidCommands.js

-describe('valid commands', () => {
-  it('just works', () => {
-    //
-  });
-});
-
-const singleContainerApp = {
+export const singleScreenApp = {
   container: {
-    key: 'com.example.FirstTabContainer'
+    key: 'com.example.MyScreen'
   }
 };
 
-const tabBasedApp = {
+export const tabBasedApp = {
   tabs: [
     {
       container: {
-        key: 'com.example.FirstTabContainer'
+        key: 'com.example.FirstTab'
       }
     },
     {
       container: {
-        key: 'com.example.SecondTabContainer'
+        key: 'com.example.SecondTab'
       }
     },
     {
       container: {
-        key: 'com.example.FirstTabContainer'
+        key: 'com.example.FirstTab'
       }
     }
   ]
 };
 
-const singleWithSideMenu = {
+export const singleWithSideMenu = {
   container: {
-    key: 'com.example.MyContainer'
+    key: 'com.example.MyScreen'
   },
   sideMenu: {
     left: {
   }
 };
 
-const singleWithRightSideMenu = {
+export const singleWithRightSideMenu = {
   container: {
-    key: 'com.example.MyContainer'
+    key: 'com.example.MyScreen'
   },
   sideMenu: {
     right: {
   }
 };
 
-const singleWithBothMenus = {
+export const singleWithBothMenus = {
   container: {
-    key: 'com.example.MyContainer'
+    key: 'com.example.MyScreen'
   },
   sideMenu: {
     left: {
   }
 };
 
-const tabBasedWithSideMenu = {
+export const tabBasedWithSideMenu = {
   tabs: [
     {
       container: {
-        key: 'com.example.FirstTabContainer'
+        key: 'com.example.FirstTab'
       }
     },
     {
       container: {
-        key: 'com.example.SecondTabContainer'
+        key: 'com.example.SecondTab'
       }
     },
     {
       container: {
-        key: 'com.example.FirstTabContainer'
+        key: 'com.example.FirstTab'
       }
     }
   ],

src/providers/__mocks__/UniqueIdProvider.js

 export function uniqueId(prefix) {
-  return `${prefix}123`;
+  return `${prefix}UNIQUE`;
 }