Question

I’m new to unit tests for my own projects, so this is my first attempt to write a unit test from scratch. I’m using python, and the unittest module. The TodoList class being tested here is a wrapper for actual lists, with a few extra methods for stuff like saving to disc. It also defines a few methods for getting items by their ID in the list (which isn’t the same as the list index).

Tests (I’ve cut out a few helper methods, and a good few tests for the sake of not having people to scroll forever):

class TodoListTests(unittest.TestCase):

    def setUp(self):
        self.testdata = open("./testdata.json", "r")
        self.testdata_text = self.testdata.read()
        self.testdata.close()

    def tearDown(self):
        try:
            os.remove("./todo.json")
        except OSError:
            # File not created, no need to delete.
            pass

    def create_todolist_and_safe_list(self):
        self.create_data_file()
        self.todolist = todolist.TodoList("./todo.json")
        self.list = json.loads(self.testdata_text)

    def create_data_file(self):
        datafile = open("./todo.json", "w")
        datafile.write(self.testdata_text)
        datafile.close()

    # Snip out a few more helper methods

    def test_loop(self):
        self.create_todolist_and_safe_list()
        test_list = []
        for item in self.todolist:
        test_list.append(item)

        self.assertEquals(test_list, self.list)


    def test_save(self):    
        self.create_todolist_and_safe_list()
        self.todolist.save()
        newfile_text = self.get_data_file_as_string()
        self.assertEquals(newfile_text, self.testdata_text)

    # Snip out the rest of the tests.

Full link to source

Answer 1

I think that you are going in the right way. But I will send some suggestions;

• Move the self.testdata.close() from setUp() to the tearDown() function.
• Surround the others open/close with try/finally blocks. So, if a file didn’t open with success it will be closed.

    try:
        file.open()
    finally:
        file.close()

• Organize better your test folders. I suggest you to create a folder named _tests and inside this folder you should put the tests module (at your case you only have one module). Then, for each module create a folder with the name of the module and puts the files used by the tests of a module inside this folder.

To know more about TDD and tests you should read the book Test Driven Development: By Example