public void Operations_Are_Batched()
{
User user1 = null;
User user2 = null;
// Run within an async context to make sure we won't deadlock
AsyncContext.Run(async() =>
{
var loader = new BatchDataLoader <int, User>(Users.GetUsersByIdAsync);
// Start async tasks to load by ID
var task1 = loader.LoadAsync(1);
var task2 = loader.LoadAsync(2);
// Dispatch loading
loader.Dispatch();
// Now await tasks
user1 = await task1;
user2 = await task2;
});
user1.ShouldNotBeNull();
user2.ShouldNotBeNull();
user1.UserId.ShouldBe(1);
user2.UserId.ShouldBe(2);
// This should have been called only once to load in a single batch
Users.GetUsersByIdCalledCount.ShouldBe(1, "Operations were not batched");
}
public async Task All_Requested_Keys_Should_Be_Cached()
{
var nullObjectUser = new User();
User user1 = null;
User user2 = null;
User user3 = null;
// There is no user with the ID of 3
// 3 will not be in the returned Dictionary, so the DataLoader should use the specified default value
var loader = new BatchDataLoader <int, User>(Users.GetUsersByIdAsync, defaultValue: nullObjectUser);
// Start async tasks to load by ID
var task1 = loader.LoadAsync(1);
var task2 = loader.LoadAsync(2);
var task3 = loader.LoadAsync(3);
// Dispatch loading
loader.Dispatch();
// Now await tasks
user1 = await task1;
user2 = await task2;
user3 = await task3;
// Load key 3 again.
var task3b = loader.LoadAsync(3);
task3b.Status.ShouldBe(TaskStatus.RanToCompletion,
"Should be cached because it was requested in the first batch even though it wasn't in the result dictionary");
loader.Dispatch();
var user3b = await task3b;
user3.ShouldBeSameAs(nullObjectUser, "The DataLoader should use the supplied default value");
Users.GetUsersByIdCalledCount.ShouldBe(1, "Results should have been cached from first batch");
}
public void Results_Are_Cached()
{
User user1 = null;
User user2 = null;
User user3 = null;
// Run within an async context to make sure we won't deadlock
AsyncContext.Run(async() =>
{
var loader = new BatchDataLoader <int, User>(Users.GetUsersByIdAsync);
// Start async tasks to load by ID
var task1 = loader.LoadAsync(1);
var task2 = loader.LoadAsync(2);
// Dispatch loading
loader.Dispatch();
// Now await tasks
user1 = await task1;
user2 = await task2;
var task3 = loader.LoadAsync(1);
task3.Status.ShouldBe(TaskStatus.RanToCompletion,
"Task should already be complete because value comes from cache");
// This should not actually run the fetch delegate again
loader.Dispatch();
user3 = await task3;
});
user3.ShouldBeSameAs(user1);
Users.GetUsersByIdCalledCount.ShouldBe(1);
}
public async Task Keys_Are_DeDuped()
{
var loader = new BatchDataLoader <int, User>(Users.GetUsersByIdAsync);
// Start async tasks to load duplicate IDs
var task1 = loader.LoadAsync(1);
var task2 = loader.LoadAsync(1);
// Dispatch loading
loader.Dispatch();
// Now await tasks
var user1 = await task1;
var user1b = await task2;
Users.GetUsersByIdCalledCount.ShouldBe(1);
Users.GetUsersById_UserIds.Count().ShouldBe(1, "The keys passed to the fetch delegate should be de-duplicated");
}
public async Task ToDictionary_Exception()
{
var loader = new BatchDataLoader <int, User>(Users.GetDuplicateUsersAsync, x => x.UserId);
// Start async tasks to load by ID
var task1 = loader.LoadAsync(1);
var task2 = loader.LoadAsync(2);
// Dispatch loading
loader.Dispatch();
try
{
// Now await tasks
var user1 = await task1;
var user2 = await task2;
}
catch (ArgumentException ex) when(ex.Message == "An item with the same key has already been added. Key: 1")
{
// This is the exception we should get
}
}
public void NonExistent_Key_Will_Return_Default_Value()
{
var nullObjectUser = new User();
User user1 = null;
User user2 = null;
User user3 = null;
// Run within an async context to make sure we won't deadlock
AsyncContext.Run(async() =>
{
// There is no user with the ID of 3
// 3 will not be in the returned Dictionary, so the DataLoader should use the specified default value
var loader = new BatchDataLoader <int, User>(Users.GetUsersByIdAsync, defaultValue: nullObjectUser);
// Start async tasks to load by ID
var task1 = loader.LoadAsync(1);
var task2 = loader.LoadAsync(2);
var task3 = loader.LoadAsync(3);
// Dispatch loading
loader.Dispatch();
// Now await tasks
user1 = await task1;
user2 = await task2;
user3 = await task3;
});
user1.ShouldNotBeNull();
user2.ShouldNotBeNull();
user3.ShouldNotBeNull();
user1.UserId.ShouldBe(1);
user2.UserId.ShouldBe(2);
user3.ShouldBeSameAs(nullObjectUser, "The DataLoader should use the supplied default value");
}