Improved descriptions

snippets/symmetricDifference.md

@@ -1,6 +1,6 @@
 ### symmetricDifference
 
-Returns the symmetric difference between two arrays.
+Returns the symmetric difference between two arrays, without filtering out duplicate values.
 
 Create a `Set` from each array, then use `Array.filter()` on each of them to only keep values not contained in the other.
 

snippets/uniqueSymmetricDifference.md

@@ -1,6 +1,6 @@
 ### uniqueSymmetricDifference
 
-Returns the unique symmetric difference between two arrays.
+Returns the unique symmetric difference between two arrays, not containing duplicate values from either array.
 
 Use `Array.filter()` and `Array.includes()` on each array to remove values contained in the other, then create a `Set` from the results, removing duplicate values.
 

test/symmetricDifference/symmetricDifference.test.js

@@ -7,3 +7,6 @@ test('symmetricDifference is a Function', () => {
 test('Returns the symmetric difference between two arrays.', () => {
   expect(symmetricDifference([1, 2, 3], [1, 2, 4])).toEqual([3, 4]);
 });
+test('Returns duplicates from one array', () => {
+  expect(symmetricDifference([1, 2, 2], [1, 3, 1])).toEqual([2, 2, 3]);
+});