Initial import

.formatter.exs

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+# Used by "mix format"
+[
+  inputs: ["mix.exs", "{config,lib,test}/**/*.{ex,exs}"]
+]

.gitignore

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+# The directory Mix will write compiled artifacts to.
+/_build/
+
+# If you run "mix test --cover", coverage assets end up here.
+/cover/
+
+# The directory Mix downloads your dependencies sources to.
+/deps/
+
+# Where 3rd-party dependencies like ExDoc output generated docs.
+/doc/
+
+# Ignore .fetch files in case you like to edit your project deps locally.
+/.fetch
+
+# If the VM crashes, it generates a dump, let's ignore it too.
+erl_crash.dump
+
+# Also ignore archive artifacts (built via "mix archive.build").
+*.ez
+
+# Ignore package tarball (built via "mix hex.build").
+time_machine-*.tar
+

.travis.yml

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+language: elixir
+elixir:
+  - 1.6.0
+otp_release:
+  - 20.0
+script: mix analyze
+cache:
+  directories:
+    - _build
+    - deps

CHANGELOG.md

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+# Changelog
+
+## 0.1.0
+
+* Initial import

LICENSE.md

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+# MIT License
+
+Copyright (c) 2018 SQUARE ENIX LTD.
+
+Permission is hereby granted, free of charge, to any person obtaining
+a copy of this software and associated documentation files (the
+"Software"), to deal in the Software without restriction, including
+without limitation the rights to use, copy, modify, merge, publish,
+distribute, sublicense, and/or sell copies of the Software, and to
+permit persons to whom the Software is furnished to do so, subject to
+the following conditions:
+
+The above copyright notice and this permission notice shall be
+included in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

README.md

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+# TimeMachinex
+## Installation
+
+If [available in Hex](https://hex.pm/docs/publish), the package can be installed
+by adding `time_machine` to your list of dependencies in `mix.exs`:
+
+```elixir
+def deps do
+  [
+    {:time_machinex, "~> 0.1.0"}
+  ]
+end
+```
+
+## Introduction
+TimeMachinex is just a managed clock around the system clock which works with `DateTime.t()` types.
+
+### Configuration
+Configuring TimeMachine is very simple. What you generally want to do is to configure the *SystemClock* for `:prod` and `:dev` env:
+
+```elixir
+config :time_machinex, TimeMachinex, adapter: TimeMachinex.SystemClock
+```
+
+and the *ManagedClock* in the `:test` env:
+```elixir
+config :time_machinex, TimeMachinex, adapter: TimeMachinex.ManagedClock
+```
+
+### Usage
+Whenever you need the current system time just replace the standard `DateTime.utc_now/0` call with a `TimeMachinex.now/0` call.
+
+In `:prod` and `:dev` this will have no real side effects, since the `now/0` function is just an alias for the `DateTime.utc_now/0` thanks to the inline compilation attribute.
+
+The magic happens in the `:test` environment since the `TimeMachinex.ManagedClock` adapter will kick in (if configured properly).
+The only thing you need to do in your tests is to start the *ManagedClock*:
+
+    ex(1)> TimeMachinex.ManagedClock.start()
+    {:ok, #PID<0.190.0>}
+
+when it starts it is configured with the current time:
+
+    iex(2)> TimeMachinex.ManagedClock.now()
+    #DateTime<2018-01-30 15:51:33.689925Z>
+
+but now all the calls to `TimeMachinex.now/0` will read the time from the *ManagedClock*
+
+    iex(3)> TimeMachinex.now()
+    #DateTime<2018-01-30 15:51:33.689925Z>
+
+which means that you can manipulate, simulate the time passing and test the time used in your production code.
+
+And yes, you stopped the time!
+
+    iex(4)> TimeMachinex.now()
+    #DateTime<2018-01-30 15:51:33.689925Z>
+    iex(5)> TimeMachinex.now()
+    #DateTime<2018-01-30 15:51:33.689925Z>
+
+If you want to update the TimeMachinex with the current time again (to simulate time passing) you can just:
+
+    iex(7)> TimeMachinex.ManagedClock.set()
+    :ok
+    iex(8)> TimeMachinex.now()
+    #DateTime<2018-01-30 15:54:43.641350Z>
+
+or you may just want to set a specific time and wait for Marty McFly:
+
+    iex(9)> TimeMachinex.ManagedClock.set(DateTime.from_naive!(~N[1985-10-26 09:00:00], "Etc/UTC"))
+    :ok
+
+    iex(10)> TimeMachinex.now()
+    #DateTime<1985-10-26 09:00:00Z>
+
+Happy time travel!

config/config.exs

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+use Mix.Config

coveralls.json

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+{
+  "skip_files": [],
+  "custom_stop_words": [
+    "\\\\\\\\",
+    "defdelegate"
+  ]
+}

lib/time_machinex.ex

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+defmodule TimeMachinex do
+  @moduledoc """
+   Define a generic clock api
+  """
+  @spec now() :: DateTime.t()
+  def now do
+    adapter().now
+  end
+
+  defp adapter do
+    case Application.fetch_env(:time_machinex, TimeMachinex) do
+      {:ok, config} -> Keyword.get(config, :adapter, TimeMachinex.SystemClock)
+      :error -> TimeMachinex.SystemClock
+    end
+  end
+end

lib/time_machinex/adapter.ex

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+defmodule TimeMachinex.Adapter do
+  @moduledoc """
+  Clock behaviour definition
+  """
+
+  @callback now() :: DateTime.t()
+end

lib/time_machinex/adapters/managed_clock.ex

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+defmodule TimeMachinex.ManagedClock do
+  @moduledoc """
+  Programmable clock
+  """
+  @behaviour TimeMachinex.Adapter
+
+  @spec start() :: {:ok, pid}
+  def start, do: Agent.start_link(&DateTime.utc_now/0, name: __MODULE__)
+
+  @spec set(DateTime.t()) :: :ok
+  def set(new_time \\ DateTime.utc_now()), do: Agent.update(__MODULE__, fn _ -> new_time end)
+
+  @impl TimeMachinex.Adapter
+  def now, do: Agent.get(__MODULE__, & &1)
+end

lib/time_machinex/adapters/system_clock.ex

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+defmodule TimeMachinex.SystemClock do
+  @moduledoc """
+  System clock implementation
+  """
+  @compile {:inline, now: 0}
+  @behaviour TimeMachinex.Adapter
+
+  @impl TimeMachinex.Adapter
+  def now, do: DateTime.utc_now()
+end

mix.exs

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+defmodule TimeMachinex.MixProject do
+  use Mix.Project
+
+  @version "0.1.0"
+  @description "Time machine clock to simplify time testing"
+
+  def project do
+    [
+      app: :time_machinex,
+      version: @version,
+      description: @description,
+      elixir: "~> 1.6",
+      start_permanent: Mix.env() == :prod,
+      deps: deps(),
+      package: package(),
+
+      # Testing
+      test_coverage: [tool: ExCoveralls],
+      dialyzer: [ignore_warnings: "dialyzer.ignore-warnings", plt_add_deps: true],
+
+      # Docs
+      name: "TimeMachinex",
+      docs: [extras: ["README.md", "CHANGELOG.md", "LICENSE.md"]]
+    ]
+  end
+
+  defp package do
+    [
+      name: :time_machinex,
+      files: [
+        # Project files
+        "mix.exs",
+        "README.md",
+        "CHANGELOG.md",
+        "LICENSE.md",
+        # TimeMachinex
+        "lib/time_machinex.ex",
+        "lib/time_machinex"
+      ],
+      maintainers: [
+        "Antonio Sagliocco",
+        "Elliott Hilaire",
+        "Francesco Grammatico",
+        "Ian Luites",
+        "Ricardo Perez",
+        "Tatsuya Ono"
+      ],
+      licenses: ["MIT"],
+      links: %{"GitHub" => "https://github.com/shinyscorpion/time_machinex"}
+    ]
+  end
+
+  def application do
+    [
+      extra_applications: [:logger]
+    ]
+  end
+
+  # Run "mix help deps" to learn about dependencies.
+  defp deps do
+    [
+      {:analyze, "~> 0.0.9", only: [:dev, :test]}
+    ]
+  end
+end

mix.lock

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+%{
+  "analyze": {:hex, :analyze, "0.0.9", "0fa122220264e18d9f0c931d81440b030a02f9037bc8f13ea21bbc640a0f88ca", [], [{:credo, "~> 0.8", [hex: :credo, repo: "hexpm", optional: false]}, {:dialyxir, "~> 0.5", [hex: :dialyxir, repo: "hexpm", optional: false]}, {:ex_doc, "~> 0.18", [hex: :ex_doc, repo: "hexpm", optional: false]}, {:excoveralls, "~> 0.8", [hex: :excoveralls, repo: "hexpm", optional: false]}, {:hackney, "~> 1.10", [hex: :hackney, repo: "hexpm", optional: false]}, {:inch_ex, "~> 0.5", [hex: :inch_ex, repo: "hexpm", optional: false]}], "hexpm"},
+  "bunt": {:hex, :bunt, "0.2.0", "951c6e801e8b1d2cbe58ebbd3e616a869061ddadcc4863d0a2182541acae9a38", [], [], "hexpm"},
+  "certifi": {:hex, :certifi, "2.0.0", "a0c0e475107135f76b8c1d5bc7efb33cd3815cb3cf3dea7aefdd174dabead064", [], [], "hexpm"},
+  "credo": {:hex, :credo, "0.8.10", "261862bb7363247762e1063713bb85df2bbd84af8d8610d1272cd9c1943bba63", [], [{:bunt, "~> 0.2.0", [hex: :bunt, repo: "hexpm", optional: false]}], "hexpm"},
+  "dialyxir": {:hex, :dialyxir, "0.5.1", "b331b091720fd93e878137add264bac4f644e1ddae07a70bf7062c7862c4b952", [], [], "hexpm"},
+  "earmark": {:hex, :earmark, "1.2.4", "99b637c62a4d65a20a9fb674b8cffb8baa771c04605a80c911c4418c69b75439", [], [], "hexpm"},
+  "ex_doc": {:hex, :ex_doc, "0.18.2", "993e0a95e9fbb790ac54ea58e700b45b299bd48bc44b4ae0404f28161f37a83e", [], [{:earmark, "~> 1.1", [hex: :earmark, repo: "hexpm", optional: false]}], "hexpm"},
+  "excoveralls": {:hex, :excoveralls, "0.8.1", "0bbf67f22c7dbf7503981d21a5eef5db8bbc3cb86e70d3798e8c802c74fa5e27", [], [{:exjsx, ">= 3.0.0", [hex: :exjsx, repo: "hexpm", optional: false]}, {:hackney, ">= 0.12.0", [hex: :hackney, repo: "hexpm", optional: false]}], "hexpm"},
+  "exjsx": {:hex, :exjsx, "4.0.0", "60548841e0212df401e38e63c0078ec57b33e7ea49b032c796ccad8cde794b5c", [], [{:jsx, "~> 2.8.0", [hex: :jsx, repo: "hexpm", optional: false]}], "hexpm"},
+  "hackney": {:hex, :hackney, "1.11.0", "4951ee019df102492dabba66a09e305f61919a8a183a7860236c0fde586134b6", [], [{:certifi, "2.0.0", [hex: :certifi, repo: "hexpm", optional: false]}, {:idna, "5.1.0", [hex: :idna, repo: "hexpm", optional: false]}, {:metrics, "1.0.1", [hex: :metrics, repo: "hexpm", optional: false]}, {:mimerl, "1.0.2", [hex: :mimerl, repo: "hexpm", optional: false]}, {:ssl_verify_fun, "1.1.1", [hex: :ssl_verify_fun, repo: "hexpm", optional: false]}], "hexpm"},
+  "idna": {:hex, :idna, "5.1.0", "d72b4effeb324ad5da3cab1767cb16b17939004e789d8c0ad5b70f3cea20c89a", [], [{:unicode_util_compat, "0.3.1", [hex: :unicode_util_compat, repo: "hexpm", optional: false]}], "hexpm"},
+  "inch_ex": {:hex, :inch_ex, "0.5.6", "418357418a553baa6d04eccd1b44171936817db61f4c0840112b420b8e378e67", [], [{:poison, "~> 1.5 or ~> 2.0 or ~> 3.0", [hex: :poison, repo: "hexpm", optional: false]}], "hexpm"},
+  "jsx": {:hex, :jsx, "2.8.3", "a05252d381885240744d955fbe3cf810504eb2567164824e19303ea59eef62cf", [], [], "hexpm"},
+  "metrics": {:hex, :metrics, "1.0.1", "25f094dea2cda98213cecc3aeff09e940299d950904393b2a29d191c346a8486", [], [], "hexpm"},
+  "mimerl": {:hex, :mimerl, "1.0.2", "993f9b0e084083405ed8252b99460c4f0563e41729ab42d9074fd5e52439be88", [], [], "hexpm"},
+  "poison": {:hex, :poison, "3.1.0", "d9eb636610e096f86f25d9a46f35a9facac35609a7591b3be3326e99a0484665", [], [], "hexpm"},
+  "ssl_verify_fun": {:hex, :ssl_verify_fun, "1.1.1", "28a4d65b7f59893bc2c7de786dec1e1555bd742d336043fe644ae956c3497fbe", [], [], "hexpm"},
+  "unicode_util_compat": {:hex, :unicode_util_compat, "0.3.1", "a1f612a7b512638634a603c8f401892afbf99b8ce93a45041f8aaca99cadb85e", [], [], "hexpm"},
+}

test/test_helper.exs

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+ExUnit.start()

test/time_machinex/adapters/managed_clock_test.exs

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+defmodule TimeMachinex.ManagedClockTest do
+  @moduledoc false
+  use ExUnit.Case, async: false
+
+  alias TimeMachinex.ManagedClock
+
+  @past ~N[1970-01-01 10:10:10]
+
+  describe "start/1" do
+    test "starts the sigleton agent" do
+      assert {:ok, _pid} = ManagedClock.start()
+      assert {:error, {:already_started, _pid}} = ManagedClock.start()
+    end
+  end
+
+  describe "now/0" do
+    setup do
+      ManagedClock.start()
+
+      :ok
+    end
+
+    test "return the time set in the time machine" do
+      now = ManagedClock.now()
+      assert now < DateTime.utc_now()
+      assert now == ManagedClock.now()
+
+      ManagedClock.set(DateTime.from_naive!(@past, "Etc/UTC"))
+      assert DateTime.from_naive!(@past, "Etc/UTC") == ManagedClock.now()
+    end
+  end
+
+  describe "set/1" do
+    setup do
+      ManagedClock.start()
+
+      :ok
+    end
+
+    test "set the time in the time machine to the new system time as default" do
+      now = ManagedClock.now()
+
+      ManagedClock.set()
+
+      assert now < ManagedClock.now()
+    end
+
+    test "set the time in the time machine to a specific value" do
+      ManagedClock.set(DateTime.from_naive!(@past, "Etc/UTC"))
+
+      assert ManagedClock.now() < DateTime.utc_now()
+    end
+  end
+end

test/time_machinex/adapters/system_clock_test.exs

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+defmodule TimeMachinex.SystemClockTest do
+  @moduledoc false
+  use ExUnit.Case, async: false
+
+  alias TimeMachinex.SystemClock
+
+  describe "now/0" do
+    test "return the current system time" do
+      now = SystemClock.now()
+
+      assert now < SystemClock.now()
+    end
+  end
+end