Added feature of checking if task added is neither a string nor a Task object. But I also discovered that the error thrown is not checked properly.

src/task.coffee

@@ -17,10 +17,12 @@ class TaskList
     @tasks = []
     @length = 0
   add: (@name) ->
+    unless typeof @name is 'string' or @name instanceof Task
+      throw "Here's an error"
     if typeof @name is 'string'
       task = new Task 'take out garbage'
-      @tasks.push task
-    else
+      @tasks.push task    
+    if @name instanceof Task
       @tasks.push @name
     @length++
   remove: (task) ->

test/taskTest.coffee

@@ -1,5 +1,5 @@
 chai = require 'chai'
-chai.should()
+should = chai.should()
 expect = chai.expect
 
 {TaskList, Task} = require '../src/task'
@@ -36,7 +36,8 @@ describe 'Task instance', ->
 		task2.status.should.equal 'dependent'
 		task2.parent.should.equal task1
 		task1.child.should.equal task2
-		-> task2.complete().should.throw "Dependent task 'wash dishes' is not completed."
+		#-> task2.complete().should.throw "Dependent task 'wash dishes' is not completed."
+		(-> task2.complete()).should.throw "Dependent task 'wash dishes' is not completed."
 
 describe 'TaskList', ->
 	taskList = null
@@ -90,3 +91,8 @@ describe 'TaskList', ->
 """
 
 		taskList.print().should.equal desiredOutput
+	it "throws error if anything but strings or task is added", ->
+		taskList = new TaskList
+		Error = "This is an error"
+		(-> taskList.add(123123)).should.throw(Error)
+		#assert(expression, message, negateMessage, expected, actual)