MockPromise.js

class MockPromise {  
  then(fn) {    
    this.thenFn = fn    
    return this  
   }
   
   catch(fn) {    
     this.catchFn = fn    
     return this  
   }   
   
   exec(name, params) {    
     this[`${name}Fn`](params)  
   }
}