public void RetrieveItems_algorithmTest()
{
m_recentItems = new RecentItemsCache <string, int>(5);
AddNewItem("1", 6);
AddNewItem("2", 5);
AddNewItem("3", 4);
AddNewItem("4", 3);
AddNewItem("5", 2);
// At this point the cache is fully loaded. When we add another, it will have to discard
// at least the least frequently requested item.
AddNewItem("6", 1);
// So, when we add "5" again, it will have to be recomputed.
AddNewItem("5", 2);
// The question is, which one should it have discarded in order to add "5" again?
// "6" is plausible, since it has only been asked for once, while all the other
// values have been requested more. However, we want some bias towards things
// recently asked for. We'd like to see "4" as the next one chosen to remove.
AddNewItem("4", 2);
// Don't want to constrain the algorithm too closely, but after several cycles even "1" should be discarded.
AddNewItem("7", 2);
AddNewItem("8", 2);
AddNewItem("9", 2);
AddNewItem("10", 2);
AddNewItem("11", 2);
AddNewItem("1", 1);
AddItem("11", false); // most recent one should still be around.
}
public void NullInput_key()
{
// Attempt to cache a key,value pair with null key
var cache = new RecentItemsCache <string, string>(7);
cache.GetItem(null, key => { return("value"); });
}
public void NullInput_value()
{
// Cache a key,value pair with null value.
var cache = new RecentItemsCache <int, string>(7);
Assert.DoesNotThrow(() => {
cache.GetItem(0, key => { return(null); });
}, "Null value should not throw exception");
}
public void Cache_addItem()
{
Func <int, string> creator = (int key) => {
return(key.ToString());
};
var cache = new RecentItemsCache <int, string>(7);
AddNewItem <int, string>(cache, 0, creator);
}
public void Cache_reportsIfItemWasRetrievedFromCache()
{
Func <int, string> creator = key => {
return(key.ToString());
};
bool wasRetrievedFromCache;
var cache = new RecentItemsCache <int, string>(7);
cache.GetItem(0, creator, out wasRetrievedFromCache);
Assert.AreEqual(false, wasRetrievedFromCache, "Adding a new item to cache should not report it as retrieved from cache.");
cache.GetItem(0, creator, out wasRetrievedFromCache);
Assert.AreEqual(true, wasRetrievedFromCache, "Retrieving a cached item should report that it was retrieved from cache.");
}
public void Cache_matchesEqualKeyOfDifferentReference()
{
Func <MyKey, string> creator = (MyKey inputKey) => {
return(inputKey.Data + "value");
};
int capacity = 7;
var cache = new RecentItemsCache <MyKey, string>(capacity);
// Two keys: equal in data/value but of different references
var key1 = new MyKey(0);
var key2 = new MyKey(0);
AddNewItem <MyKey, string>(cache, key1, creator);
GetExistingItem <MyKey, string>(cache, key2, creator);
}
public void Cache_matchesKeyOfSameReference()
{
Func <MyKey, string> creator = (MyKey inputKey) => {
return(inputKey.Data + "value");
};
int capacity = 7;
var cache = new RecentItemsCache <MyKey, string>(capacity);
// Keys have the same Reference
var key1 = new MyKey(0);
var key2 = key1;
AddNewItem <MyKey, string>(cache, key1, creator);
GetExistingItem <MyKey, string>(cache, key2, creator);
}
public void Cache_retainsManyItems()
{
Func <int, string> creator = (int key) => {
return(key.ToString());
};
int capacity = 7;
var cache = new RecentItemsCache <int, string>(capacity);
for (int i = 0; i < capacity; i++)
{
AddNewItem <int, string>(cache, i, creator);
}
for (int i = 0; i < capacity; i++)
{
GetExistingItem <int, string>(cache, i, creator);
}
}
/// <summary>
/// Add key,value pair to cache, checking if it was newly added.
/// Will assert if computed if not expected, or did not compute if expected to.
/// </summary>
/// <param name="cache"></param>
/// <param name="key"></param>
/// <param name="creator">Delegate to create the value from key</param>
/// <param name="expectToCompute">
/// Whether should expect to need to compute the value from key using creator
/// </param>
private void AddItem <K, V>(RecentItemsCache <K, V> cache, K key, Func <K, V> creator,
bool expectToCompute)
{
bool didCompute = false;
Assert.AreEqual(creator(key), cache.GetItem(key, key1 =>
{
didCompute = true;
return(creator(key1));
}), String.Format("wrong value for {0} cached key given", didCompute?"newly":"previously"));
string errorMessage;
if (expectToCompute)
{
errorMessage = "Expected to compute value from key since it was not expected to be in the cache, but it was in the cache.";
}
else
{
errorMessage = "Did not expect to compute value from key since expected it to be in the cache, but it was not in the cache.";
}
Assert.AreEqual(expectToCompute, didCompute, errorMessage);
}
public void Caching_itemsFallOutOfCache()
{
Func <int, string> creator = (int key) => {
return(key.ToString());
};
var cacheCapacity = 7;
var cache = new RecentItemsCache <int, string>(cacheCapacity);
int valueLargerThanCacheCapacity = cacheCapacity * 3;
// Add some items, all of which should be new to the cache
for (int i = 0; i < valueLargerThanCacheCapacity; i++)
{
AddNewItem <int, string>(cache, i, creator);
}
// Adding the first few items again should not be able to retrieve them from the cache.
// They should have fallen out of the cache by now.
for (int i = 0; i < cacheCapacity; i++)
{
AddNewItem <int, string>(cache, i, creator);
}
}
private void AddNewItem <K, V>(RecentItemsCache <K, V> cache, K key, Func <K, V> creator)
{
AddItem <K, V>(cache, key, creator, true);
}
private void GetExistingItem <K, V>(RecentItemsCache <K, V> cache, K key, Func <K, V> creator)
{
AddItem <K, V>(cache, key, creator, false);
}