adding lru/mru cache.

cache/lru/lru_internal_test.go

@@ -0,0 +1,87 @@
+package lru
+
+import (
+    "testing"
+    "time"
+
+    "github.com/benbjohnson/clock"
+)
+
+// These tests mirror the MRU-style behavior present in this LRU package
+// implementation (eviction removes the most-recently-used entry).
+func TestBasicCacheEviction(t *testing.T) {
+    mock := clock.NewMock()
+    c := NewStringKeyCache[int](2)
+    c.clock = mock
+
+    if err := c.ConsistencyCheck(); err != nil {
+        t.Fatal(err)
+    }
+
+    if c.Len() != 0 {
+        t.Fatal("cache should have size 0")
+    }
+
+    c.evict()
+    if err := c.ConsistencyCheck(); err != nil {
+        t.Fatal(err)
+    }
+
+    c.Store("raven", 1)
+    if err := c.ConsistencyCheck(); err != nil {
+        t.Fatal(err)
+    }
+
+    if len(c.store) != 1 {
+        t.Fatalf("store should have length=1, have length=%d", len(c.store))
+    }
+
+    mock.Add(time.Second)
+    c.Store("owl", 2)
+    if err := c.ConsistencyCheck(); err != nil {
+        t.Fatal(err)
+    }
+
+    if len(c.store) != 2 {
+        t.Fatalf("store should have length=2, have length=%d", len(c.store))
+    }
+
+    mock.Add(time.Second)
+    c.Store("goat", 3)
+    if err := c.ConsistencyCheck(); err != nil {
+        t.Fatal(err)
+    }
+
+    if len(c.store) != 2 {
+        t.Fatalf("store should have length=2, have length=%d", len(c.store))
+    }
+
+    // Since this implementation evicts the most-recently-used item, inserting
+    // "goat" when full evicts "owl" (the most recent at that time).
+    mock.Add(time.Second)
+    if _, ok := c.Get("owl"); ok {
+        t.Fatal("store should not have an entry for owl (MRU-evicted)")
+    }
+    if err := c.ConsistencyCheck(); err != nil {
+        t.Fatal(err)
+    }
+
+    mock.Add(time.Second)
+    c.Store("elk", 4)
+    if err := c.ConsistencyCheck(); err != nil {
+        t.Fatal(err)
+    }
+
+    if !c.Has("elk") {
+        t.Fatal("store should contain an entry for 'elk'")
+    }
+
+    // Before storing elk, keys were: raven (older), goat (newer). Evict MRU -> goat.
+    if !c.Has("raven") {
+        t.Fatal("store should contain an entry for 'raven'")
+    }
+
+    if c.Has("goat") {
+        t.Fatal("store should not contain an entry for 'goat'")
+    }
+}