From 411ceb854174c5e8a2086bb4dbee079b7b37e981 Mon Sep 17 00:00:00 2001
From: Maximilian Antoni <mail@maxantoni.de>
Date: Tue, 26 Feb 2019 21:15:03 +0100
Subject: [PATCH] Fail when passing undefined as the expectation for equals

---
 lib/assertions/equals.js      | 5 +++++
 lib/assertions/equals.test.js | 4 ++--
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/lib/assertions/equals.js b/lib/assertions/equals.js
index 68ae56b2..eb416149 100644
--- a/lib/assertions/equals.js
+++ b/lib/assertions/equals.js
@@ -14,6 +14,11 @@ module.exports = function(referee) {
         // Uses arguments[2] because the function's .length is used to determine
         // the minimum required number of arguments.
         assert: function(actual, expected) {
+            if (typeof expected === "undefined") {
+                return this.fail(
+                    "Expectation for equals should not be undefined. Use assert.defined or refute.defined instead."
+                );
+            }
             return samsam.deepEqual(actual, expected);
         },
         assertMessage:
diff --git a/lib/assertions/equals.test.js b/lib/assertions/equals.test.js
index 7260d643..04b35a81 100644
--- a/lib/assertions/equals.test.js
+++ b/lib/assertions/equals.test.js
@@ -17,7 +17,7 @@ testHelper.assertionTests("assert", "equals", function(pass, fail, msg, error) {
     pass("when comparing numbers", 32, 32);
     pass("when comparing booleans", false, false);
     pass("when comparing null", null, null);
-    pass("when comparing undefined", undefined, undefined);
+    fail("when comparing undefined", undefined, undefined);
     pass("when comparing function to itself", func, func);
     fail("when comparing functions", function() {}, function() {});
     pass("when comparing array to itself", arr, arr);
@@ -292,7 +292,7 @@ testHelper.assertionTests("refute", "equals", function(pass, fail, msg, error) {
     pass("when comparing different objects", obj, {});
     pass("when comparing object to null", {}, null);
     pass("when comparing null to object", {}, null);
-    pass("when comparing object to undefined", {}, undefined);
+    fail("when comparing object to undefined", {}, undefined);
     pass("when comparing undefined to object", undefined, {});
     pass("when comparing object to false", {}, false);
     pass("when comparing false to object", false, {});