Add missing LinkedList tests (trekhleb#151)

Co-authored-by: Oleksii Trekhleb <[email protected]>

Author: mleg

src/data-structures/linked-list/__test__/LinkedList.test.js

@@ -218,6 +218,29 @@ describe('LinkedList', () => {
     expect(linkedList.find({ value: 2, customValue: 'test5' })).toBeNull();
   });
 
+  it('should find preferring callback over compare function', () => {
+    const greaterThan = (value, compareTo) => (value > compareTo ? 0 : 1);
+
+    const linkedList = new LinkedList(greaterThan);
+    linkedList.fromArray([1, 2, 3, 4, 5]);
+
+    let node = linkedList.find({ value: 3 });
+    expect(node.value).toBe(4);
+
+    node = linkedList.find({ callback: value => value < 3 });
+    expect(node.value).toBe(1);
+  });
+
+  it('should convert to array', () => {
+    const linkedList = new LinkedList();
+
+    linkedList.append(1);
+    linkedList.append(2);
+    linkedList.append(3);
+
+    expect(linkedList.toArray().join(',')).toBe('1,2,3');
+  });
+  
   it('should reverse linked list', () => {
     const linkedList = new LinkedList();