From 35fc285f9aa2b254ea23abbf1000c6bc85186ea4 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jonatan=20M=C3=A4nnchen?= <jonatan@maennchen.ch>
Date: Tue, 21 Oct 2025 01:17:18 +0200
Subject: [PATCH] fix: implements_behaviour? do not return true for any module

---
 lib/spark.ex        |  2 +-
 test/spark_test.exs | 15 +++++++++++++++
 2 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/lib/spark.ex b/lib/spark.ex
index 21ee0ea..5a43a4f 100644
--- a/lib/spark.ex
+++ b/lib/spark.ex
@@ -46,7 +46,7 @@ defmodule Spark do
 
       # never seen a module with three behaviours in real life, let alone four.
       {:behaviour, behaviours} when is_list(behaviours) ->
-        module in behaviours
+        behaviour in behaviours
 
       _ ->
         false
diff --git a/test/spark_test.exs b/test/spark_test.exs
index f0d921e..2b8fa5e 100644
--- a/test/spark_test.exs
+++ b/test/spark_test.exs
@@ -6,4 +6,19 @@ defmodule SparkTest do
   use ExUnit.Case
   doctest Spark
   doctest Spark.Options
+
+  describe inspect(&Spark.implements_behaviour?/2) do
+    test "returns true if the module implements the specified behavior" do
+      defmodule TestModule do
+        @callback foo :: any()
+
+        @behaviour TestModule
+
+        def foo, do: :ok
+      end
+
+      refute Spark.implements_behaviour?(TestModule, AnyOtherModule)
+      assert Spark.implements_behaviour?(TestModule, TestModule)
+    end
+  end
 end