Tested Stack

Mix.install([
  {:jason, "~> 1.4"},
  {:kino, "~> 0.8.0", override: true},
  {:youtube, github: "brooklinjazz/youtube"},
  {:hidden_cell, github: "brooklinjazz/hidden_cell"}
])

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Tested Stack

Previously you created a Stack GenServer. Now you’re going to re-create the Stack GenServer with a full test suite.

The Stack process should store a list as state and push/2 elements onto the stack, and pop/2 elements off of the stack like so.

{:ok, pid} = Stack.start_link([])
[:one] = Stack.push(pid, :one)
[:two, :one] = Stack.push(pid, :two)
:two = Stack.pop(pid)
:one = Stack.pop(pid)
# return no value when the stack is empty
nil = Stack.pop(pid)

Pair Testing

This will be a pair testing exercise. One student will be the tester and the other will be the implementer. The tester will write the test, and the implementer will implement the code for the test.

As the implementer you may challenge your tester to improve their tests by writing only the code necessary to make the test pass (within reason) even if it is a false-positive. This will encourage your tester to write more comprehensive tests.

Swap roles for each new test.

Create A Mix Project

Create a new mix project and use LiveShare to make it simpler to collaborate with your pair partner.

mix new stack

Copy the code below into your Stack module.

defmodule Stack do
  use GenServer

  def start_link(_opts) do
  end

  def push(pid, element) do
  end

  def pop(pid) do
  end
end

Then copy the following code into the associated test file for the Stack module.

defmodule StackTest do
  use ExUnit.Case

  describe "start_link/1" do
    test "with no configuration"
    test "with a default state"
  end

  describe "push/2" do
    test "an element onto an empty stack"
    test "an element onto a stack with one element"
    test "an element onto a stack with multiple elements"
  end

  describe "pop/1" do
    test "an empty stack"
    test "a stack with one element"
    test "a stack with multiple elements"
  end
end

Bonus: GitHub Repository

Upload your stack project to GitHub. You may add your partner as a collaborator, or they can fork the project so that you both own a copy.

Create a README that describes the purpose of the project and what you learned.

Mark As Completed

file_name = Path.basename(Regex.replace(~r/#.+/, __ENV__.file, ""), ".livemd")

save_name =
  case Path.basename(__DIR__) do
    "reading" -> "stack_reading"
    "exercises" -> "stack_exercise"
  end

progress_path = __DIR__ <> "/../progress.json"
existing_progress = File.read!(progress_path) |> Jason.decode!()

default = Map.get(existing_progress, save_name, false)

form =
  Kino.Control.form(
    [
      completed: input = Kino.Input.checkbox("Mark As Completed", default: default)
    ],
    report_changes: true
  )

Task.async(fn ->
  for %{data: %{completed: completed}} <- Kino.Control.stream(form) do
    File.write!(
      progress_path,
      Jason.encode!(Map.put(existing_progress, save_name, completed), pretty: true)
    )
  end
end)

form

Commit Your Progress

Run the following in your command line from the curriculum folder to track and save your progress in a Git commit. Ensure that you do not already have undesired or unrelated changes by running git status or by checking the source control tab in Visual Studio Code.

$ git checkout -b stack-exercise
$ git add .
$ git commit -m "finish stack exercise"
$ git push origin stack-exercise

Create a pull request from your stack-exercise branch to your solutions branch. Please do not create a pull request to the DockYard Academy repository as this will spam our PR tracker.

DockYard Academy Students Only:

Notify your teacher by including @BrooklinJazz in your PR description to get feedback. You (or your teacher) may merge your PR into your solutions branch after review.

If you are interested in joining the next academy cohort, sign up here to receive more news when it is available.

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