Add Run ExUnit Tests In A Deterministic Order as an elixir til

README.md

@@ -7,7 +7,7 @@ variety of languages and technologies. These are things that don't really
 warrant a full blog post. These are mostly things I learn by pairing with
 smart people at [Hashrocket](http://hashrocket.com/).
 
-_468 TILs and counting..._
+_469 TILs and counting..._
 
 ---
 
@@ -98,6 +98,7 @@ _468 TILs and counting..._
 - [Quitting IEx](elixir/quitting-iex.md)
 - [Replace Duplicates In A Keyword List](elixir/replace-duplicates-in-a-keyword-list.md)
 - [Reversing A List](elixir/reversing-a-list.md)
+- [Run ExUnit Tests In A Deterministic Order](elixir/run-exunit-tests-in-a-deterministic-order.md)
 - [String Interpolation With Just About Anything](elixir/string-interpolation-with-just-about-anything.md)
 - [Updating Values In A Map](elixir/updating-values-in-a-map.md)
 - [Word Lists For Atoms](elixir/word-lists-for-atoms.md)

elixir/run-exunit-tests-in-a-deterministic-order.md

@@ -0,0 +1,29 @@
+# Run ExUnit Tests In A Deterministic Order
+
+When running a file of
+[`ExUnit`](http://elixir-lang.org/docs/stable/ex_unit/ExUnit.html) tests,
+they will be executed in a pseudo-random order based on a seed value. In
+general, `ExUnit` will pick a random seed each time you run your tests. If
+you'd like to add some determinism to the order that your tests run in, you
+can specify the seed in the `ExUnit` configuration.
+
+```elixir
+ExUnit.configure seed: 42
+ExUnit.start
+
+defmodule AssertionTest do
+  use ExUnit.Case, async: true
+
+  test "the truth" do
+    assert true
+  end
+
+  test "more truth" do
+    assert 2 + 2 = 4
+  end
+end
+```
+
+[source](https://til.hashrocket.com/posts/4a7dc5fd94-run-exunit-tests-in-the-order-they-are-defined)
+
+h/t Chris Erin