add move-to-tail test

test/move-to-tail.js

@@ -0,0 +1,50 @@
+const LRU = require('../')
+const c = new LRU({ max: 5 })
+const t = require('tap')
+
+t.test('list integrity', { bail: true }, t => {
+  const e = index => ({
+    index,
+    prev: c.prev[index],
+    _: index === c.tail ? 'T' : index === c.head ? 'H' : ('' + index),
+    next: c.next[index],
+    head: c.head,
+    tail: c.tail,
+  })
+  const snap = () => {
+    const a = []
+    for (let i = 0; i < 5; i++) {
+      a.push(e(i))
+    }
+    return a
+  }
+  const integrity = (msg) => {
+    t.test(msg, { bail: false }, t => {
+      let fail = false
+      for (let i = 0; i < c.max; i++) {
+        if (i !== c.head) {
+          t.equal(c.next[c.prev[i]], i, 'n[p[i]] === i')
+        }
+        if (i !== c.tail) {
+          t.equal(c.prev[c.next[i]], i, 'p[n[i]] === i')
+        }
+      }
+      t.end()
+    })
+  }
+
+  for (let i = 0; i < 5; i++) {
+    c.set(i, i)
+  }
+
+  t.matchSnapshot(snap(), 'list after initial fill')
+  integrity('after initial fill')
+  c.moveToTail(2)
+  t.matchSnapshot(snap(), 'list after moveToTail 2')
+  integrity('after moveToTail 2')
+  c.moveToTail(4)
+  t.matchSnapshot(snap(), 'list after moveToTail 4')
+  integrity('after moveToTail 4')
+
+  t.end()
+})