add unit test for Store#hasModule(path)

Author: FranckFreiburger

Diff for: test/unit/modules.spec.js

@@ -25,6 +25,8 @@ describe('Modules', () => {
           getters: { a: state => state.a }
         })
       }).not.toThrow()
+      
+      expect(store.hasModule('hi')).toBe(true)
 
       expect(store._mutations.inc.length).toBe(2)
       expect(store.state.hi.a).toBe(1)
@@ -43,6 +45,7 @@ describe('Modules', () => {
 
       // unregister
       store.unregisterModule('hi')
+      expect(store.hasModule('hi')).toBe(false)
       expect(store.state.hi).toBeUndefined()
       expect(store.getters.a).toBeUndefined()
       expect(store._mutations.inc.length).toBe(1)