Chapter 2

Exercise: PatternMatching-1

ExUnit.start(auto_run: false)

defmodule PatternMatching1Test do
  use ExUnit.Case

  test "will match" do
    a = [1, 2, 3]
    a = 4
    4 = a
    a = [[1, 2, 3]]
    [a] = [[1, 2, 3]]
  end

  test "will not match" do
    assert_raise(MatchError, fn -> [a, b] = [1, 2, 3] end)
    assert_raise(MatchError, fn -> [[a]] = [[1, 2, 3]] end)
  end
end

ExUnit.run()

Exercise: PatternMatching-2

ExUnit.start(auto_run: false)

defmodule PatternMatching2Test do
  use ExUnit.Case

  test "will match" do
    [a, b, a] = [1, 2, 1]
  end

  test "will not match" do
    assert_raise(MatchError, fn -> [a, b, a] = [1, 2, 3] end)
    assert_raise(MatchError, fn -> [a, b, a] = [1, 1, 2] end)
  end
end

ExUnit.run()

Exercise: PatternMatching-3

ExUnit.start(auto_run: false)

defmodule PatternMatching3Test do
  use ExUnit.Case

  setup do
    {:ok, a: 2}
  end

  describe "will match" do
    test "a = 1", %{a: a} do
      a = 1
    end

    test "^a = 2", %{a: a} do
      ^a = 2
    end
  end

  describe "will not match" do
    test "[a, b, a] = [1, 2, 3]", %{a: a} do
      assert_raise(MatchError, fn -> [a, b, a] = [1, 2, 3] end)
    end

    test "[a, b, a] = [1, 1, 2]", %{a: a} do
      assert_raise(MatchError, fn -> [a, b, a] = [1, 1, 2] end)
    end

    test "^a = 1", %{a: a} do
      assert_raise(MatchError, fn -> ^a = 1 end)
    end

    test "^a = 2 - a", %{a: a} do
      assert_raise(MatchError, fn -> ^a = 2 - a end)
    end
  end
end

ExUnit.run()