test: refactor test-timers-linked-list.js

* check that empty linked lists have identical properties
* `assert.equal()` -> `assert.strictEqual()`
* `var` -> `const`

PR-URL: #8193
Reviewed-By: Jeremiah Senkpiel <fishrock123@rocketmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Michaël Zasso <mic.besace@gmail.com>
Reviewed-By: Franziska Hinkelmann <franziska.hinkelmann@gmail.com>

Author: Trott

test/parallel/test-timers-linked-list.js

@@ -9,11 +9,11 @@ const internalL = require('internal/linkedlist');
 
 assert.strictEqual(L, internalL);
 
-var list = { name: 'list' };
-var A = { name: 'A' };
-var B = { name: 'B' };
-var C = { name: 'C' };
-var D = { name: 'D' };
+const list = { name: 'list' };
+const A = { name: 'A' };
+const B = { name: 'B' };
+const C = { name: 'C' };
+const D = { name: 'D' };
 
 
 L.init(list);
@@ -23,63 +23,61 @@ L.init(C);
 L.init(D);
 
 assert.ok(L.isEmpty(list));
-assert.equal(null, L.peek(list));
+assert.strictEqual(null, L.peek(list));
 
 L.append(list, A);
 // list -> A
-assert.equal(A, L.peek(list));
+assert.strictEqual(A, L.peek(list));
 
 L.append(list, B);
 // list -> A -> B
-assert.equal(A, L.peek(list));
+assert.strictEqual(A, L.peek(list));
 
 L.append(list, C);
 // list -> A -> B -> C
-assert.equal(A, L.peek(list));
+assert.strictEqual(A, L.peek(list));
 
 L.append(list, D);
 // list -> A -> B -> C -> D
-assert.equal(A, L.peek(list));
+assert.strictEqual(A, L.peek(list));
 
-var x = L.shift(list);
-assert.equal(A, x);
+assert.strictEqual(A, L.shift(list));
 // list -> B -> C -> D
-assert.equal(B, L.peek(list));
+assert.strictEqual(B, L.peek(list));
 
-x = L.shift(list);
-assert.equal(B, x);
+assert.strictEqual(B, L.shift(list));
 // list -> C -> D
-assert.equal(C, L.peek(list));
+assert.strictEqual(C, L.peek(list));
 
 // B is already removed, so removing it again shouldn't hurt.
 L.remove(B);
 // list -> C -> D
-assert.equal(C, L.peek(list));
+assert.strictEqual(C, L.peek(list));
 
 // Put B back on the list
 L.append(list, B);
 // list -> C -> D -> B
-assert.equal(C, L.peek(list));
+assert.strictEqual(C, L.peek(list));
 
 L.remove(C);
 // list -> D -> B
-assert.equal(D, L.peek(list));
+assert.strictEqual(D, L.peek(list));
 
 L.remove(B);
 // list -> D
-assert.equal(D, L.peek(list));
+assert.strictEqual(D, L.peek(list));
 
 L.remove(D);
 // list
-assert.equal(null, L.peek(list));
+assert.strictEqual(null, L.peek(list));
 
 
 assert.ok(L.isEmpty(list));
 
 
 L.append(list, D);
 // list -> D
-assert.equal(D, L.peek(list));
+assert.strictEqual(D, L.peek(list));
 
 L.append(list, C);
 L.append(list, B);
@@ -90,21 +88,24 @@ L.append(list, A);
 L.append(list, C);
 
 // list -> D -> B -> A -> C
-assert.equal(D, L.shift(list));
+assert.strictEqual(D, L.shift(list));
 // list -> B -> A -> C
-assert.equal(B, L.peek(list));
-assert.equal(B, L.shift(list));
+assert.strictEqual(B, L.peek(list));
+assert.strictEqual(B, L.shift(list));
 // list -> A -> C
-assert.equal(A, L.peek(list));
-assert.equal(A, L.shift(list));
+assert.strictEqual(A, L.peek(list));
+assert.strictEqual(A, L.shift(list));
 // list -> C
-assert.equal(C, L.peek(list));
-assert.equal(C, L.shift(list));
+assert.strictEqual(C, L.peek(list));
+assert.strictEqual(C, L.shift(list));
 // list
 assert.ok(L.isEmpty(list));
 
 const list2 = L.create();
 const list3 = L.create();
 assert.ok(L.isEmpty(list2));
 assert.ok(L.isEmpty(list3));
-assert.ok(list2 != list3);
+
+// Objects should have identical keys/properties, but be different objects.
+assert.deepStrictEqual(list2, list3);
+assert.notStrictEqual(list2, list3);