feat(core): add referenceNotEqual TDD implementation

chai-immutable.js

@@ -891,6 +891,31 @@
     }
   };
 
+  /**
+   * ### .referenceNotEqual(actual, expected)
+   *
+   * Asserts that the reference of `actual` is not equivalent to the reference of
+   * `expected`. This method preserves the original behavior of chai's notEqual.
+   *
+   * Reasons for this are described in #210.
+   *
+   * ```js
+   * const a = List.of(1, 2, 3);
+   * const b = a
+   * const c = List.of(1, 2, 3);
+   * assert.referenceNotEqual(a, b); // false
+   * assert.referenceNotEqual(a, c); // true
+   * ```
+   *
+   * @name referenceEqual
+   * @param {Collection} actual
+   * @param {Collection} expected
+   * @namespace Assert
+   * @api public
+   */
+
+  assert.referenceNotEqual = originalNotEqual;
+
   /**
    * ### .sizeOf(collection, length)
    *

test/test.js

@@ -993,6 +993,22 @@ describe('chai-immutable', function() {
       });
     });
 
+    describe('referenceNotEqual assertion', function() {
+      it('should pass for different immutable collections with equal values', function() {
+        const list1 = List.of(1, 2, 3);
+        const list2 = List.of(1, 2, 3);
+
+        assert.referenceNotEqual(list1, list2);
+      });
+
+      it('should not pass for different immutable collections with equal values', function() {
+        const list1 = List.of(1, 2, 3);
+        const list2 = list1;
+
+        fail(() => assert.referenceNotEqual(list1, list2));
+      });
+    });
+
     describe('unoverridden strictEqual and deepEqual assertions', function() {
       it('should pass given equal values', function() {
         assert.strictEqual(list3, List.of(1, 2, 3));