TDD with Livebook

Adolfo Neto - Apr 27 '22 -

- Dev Community

I have just published a video about doing TDD with Livebook:

If you are not a video person, take a look at the notebook here.

If you can run an instance of livebook, click here:

The code I typed was that of a very simple calculator. Every function was written after a test for that function was written.

defmodule Calculator do
  def add(a, b) do
    a + b
  end

  def multiply(a, b) do
    a * b
  end
end

Unfortunately, Livebook seems to force us to put the tests below the code that is being tested.

And, as Bro0klin Myers explained here, you have to add:

ExUnit.start(auto_run: false)

to the beginning of your test code.

You also have to put this line in your test module:

  use ExUnit.Case, async: false

And you have to finish your test code with this line:

ExUnit.run()

The content for the test code cell is:

ExUnit.start(auto_run: false)

defmodule CalcutorTest do
  use ExUnit.Case, async: false

  describe "Testing the addition function" do
    test "2 plus 3 is 5" do
      assert Calculator.add(2, 3) == 5
    end

    test "2 plus 2 is 4" do
      assert Calculator.add(2, 2) == 4
    end
  end

  describe "Testing the multiplication function" do
    test "2 times 3 is 6" do
      assert Calculator.multiply(2, 3) == 6
    end

    test "2 times 20 is 40" do
      assert Calculator.multiply(2, 20) == 40
    end
  end
end

ExUnit.run()

What do you think? Is it a good idea to do TDD with Liveview?