From 943d3abca471a6b96e0b3392fe904c11428d7cbf Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=C5=81ukasz=20Jan=20Niemier?= <lukasz@supabase.io>
Date: Tue, 5 Nov 2024 16:47:44 +0100
Subject: [PATCH] test: add assertion testing if value passes eventually

---
 test/supavisor/prom_ex_test.exs |  6 ++---
 test/support/asserts.ex         | 41 +++++++++++++++++++++++++++++++++
 2 files changed, 44 insertions(+), 3 deletions(-)
 create mode 100644 test/support/asserts.ex

diff --git a/test/supavisor/prom_ex_test.exs b/test/supavisor/prom_ex_test.exs
index df684260..b489f44f 100644
--- a/test/supavisor/prom_ex_test.exs
+++ b/test/supavisor/prom_ex_test.exs
@@ -2,6 +2,8 @@ defmodule Supavisor.PromExTest do
   use ExUnit.Case, async: true
   use Supavisor.DataCase
 
+  import Supavisor.Asserts
+
   alias Supavisor.Monitoring.PromEx
 
   @tenant "prom_tenant"
@@ -31,9 +33,7 @@ defmodule Supavisor.PromExTest do
     :ok = GenServer.stop(proxy)
     :ok = Supavisor.stop({{:single, @tenant}, user, :transaction, db_name, nil})
 
-    Process.sleep(3000)
-
-    refute PromEx.get_metrics() =~ "tenant=\"#{@tenant}\""
+    refute_eventually(10, fn -> PromEx.get_metrics() =~ "tenant=\"#{@tenant}\"" end)
   end
 
   test "clean_string/1 removes extra spaces from metric string" do
diff --git a/test/support/asserts.ex b/test/support/asserts.ex
new file mode 100644
index 00000000..d0e720b9
--- /dev/null
+++ b/test/support/asserts.ex
@@ -0,0 +1,41 @@
+defmodule Supavisor.Asserts do
+  @doc """
+  Asserts that `function` will eventually success. Fails otherwise.
+
+  It performs `repeats` checks with `delay` milliseconds between each check.
+  """
+  def assert_eventually(repeats \\ 5, delay \\ 1000, function)
+
+  def assert_eventually(0, _, _) do
+    raise ExUnit.AssertionError, message: "Expected function to return truthy value"
+  end
+
+  def assert_eventually(n, delay, func) do
+    if func.() do
+      :ok
+    else
+      Process.sleep(delay)
+      assert_eventually(n - 1, delay, func)
+    end
+  end
+
+  @doc """
+  Asserts that `function` will eventually fail. Fails otherwise.
+
+  It performs `repeats` checks with `delay` milliseconds between each check.
+  """
+  def refute_eventually(repeats \\ 5, delay \\ 1000, function)
+
+  def refute_eventually(0, _, _) do
+    raise ExUnit.AssertionError, message: "Expected function to return falsey value"
+  end
+
+  def refute_eventually(n, delay, func) do
+    if func.() do
+      Process.sleep(delay)
+      refute_eventually(n - 1, delay, func)
+    else
+      :ok
+    end
+  end
+end