How to mock an async repository with Entity Framework Core
Thanks to @Nkosi for pointing me to a link with an example of doing the same thing in EF 6: https://msdn.microsoft.com/en-us/library/dn314429.aspx. This didn't work exactly as-is with EF Core, but I was able to start with it and make modifications to get it working. Below are the test classes that I created to "mock" IAsyncQueryProvider:
internal class TestAsyncQueryProvider<TEntity> : IAsyncQueryProvider
{
private readonly IQueryProvider _inner;
internal TestAsyncQueryProvider(IQueryProvider inner)
{
_inner = inner;
}
public IQueryable CreateQuery(Expression expression)
{
return new TestAsyncEnumerable<TEntity>(expression);
}
public IQueryable<TElement> CreateQuery<TElement>(Expression expression)
{
return new TestAsyncEnumerable<TElement>(expression);
}
public object Execute(Expression expression)
{
return _inner.Execute(expression);
}
public TResult Execute<TResult>(Expression expression)
{
return _inner.Execute<TResult>(expression);
}
public IAsyncEnumerable<TResult> ExecuteAsync<TResult>(Expression expression)
{
return new TestAsyncEnumerable<TResult>(expression);
}
public Task<TResult> ExecuteAsync<TResult>(Expression expression, CancellationToken cancellationToken)
{
return Task.FromResult(Execute<TResult>(expression));
}
}
internal class TestAsyncEnumerable<T> : EnumerableQuery<T>, IAsyncEnumerable<T>, IQueryable<T>
{
public TestAsyncEnumerable(IEnumerable<T> enumerable)
: base(enumerable)
{ }
public TestAsyncEnumerable(Expression expression)
: base(expression)
{ }
public IAsyncEnumerator<T> GetEnumerator()
{
return new TestAsyncEnumerator<T>(this.AsEnumerable().GetEnumerator());
}
IQueryProvider IQueryable.Provider
{
get { return new TestAsyncQueryProvider<T>(this); }
}
}
internal class TestAsyncEnumerator<T> : IAsyncEnumerator<T>
{
private readonly IEnumerator<T> _inner;
public TestAsyncEnumerator(IEnumerator<T> inner)
{
_inner = inner;
}
public void Dispose()
{
_inner.Dispose();
}
public T Current
{
get
{
return _inner.Current;
}
}
public Task<bool> MoveNext(CancellationToken cancellationToken)
{
return Task.FromResult(_inner.MoveNext());
}
}
And here is my updated test case that uses these classes:
[Fact]
public async Task GetCompanyProductURLAsync_ReturnsNullForInvalidCompanyProduct()
{
var companyProducts = Enumerable.Empty<CompanyProductUrl>().AsQueryable();
var mockSet = new Mock<DbSet<CompanyProductUrl>>();
mockSet.As<IAsyncEnumerable<CompanyProductUrl>>()
.Setup(m => m.GetEnumerator())
.Returns(new TestAsyncEnumerator<CompanyProductUrl>(companyProducts.GetEnumerator()));
mockSet.As<IQueryable<CompanyProductUrl>>()
.Setup(m => m.Provider)
.Returns(new TestAsyncQueryProvider<CompanyProductUrl>(companyProducts.Provider));
mockSet.As<IQueryable<CompanyProductUrl>>().Setup(m => m.Expression).Returns(companyProducts.Expression);
mockSet.As<IQueryable<CompanyProductUrl>>().Setup(m => m.ElementType).Returns(companyProducts.ElementType);
mockSet.As<IQueryable<CompanyProductUrl>>().Setup(m => m.GetEnumerator()).Returns(() => companyProducts.GetEnumerator());
var contextOptions = new DbContextOptions<SaasDispatcherDbContext>();
var mockContext = new Mock<SaasDispatcherDbContext>(contextOptions);
mockContext.Setup(c => c.Set<CompanyProductUrl>()).Returns(mockSet.Object);
var entityRepository = new EntityRepository<CompanyProductUrl>(mockContext.Object);
var service = new CompanyProductService(entityRepository);
var result = await service.GetCompanyProductURLAsync(Guid.NewGuid(), "wot", Guid.NewGuid());
Assert.Null(result);
}
Try to use my Moq/NSubstitute/FakeItEasy extension MockQueryable: supported all Sync/Async operations (see more examples here)
//1 - create a List<T> with test items
var users = new List<UserEntity>()
{
new UserEntity,
...
};
//2 - build mock by extension
var mock = users.AsQueryable().BuildMock();
//3 - setup the mock as Queryable for Moq
_userRepository.Setup(x => x.GetQueryable()).Returns(mock.Object);
//3 - setup the mock as Queryable for NSubstitute
_userRepository.GetQueryable().Returns(mock);
DbSet also supported
//2 - build mock by extension
var mock = users.AsQueryable().BuildMockDbSet();
//3 - setup DbSet for Moq
var userRepository = new TestDbSetRepository(mock.Object);
//3 - setup DbSet for NSubstitute
var userRepository = new TestDbSetRepository(mock);
Notes:
- AutoMapper is also supported from 1.0.4 ver
- DbQuery supported from 1.1.0 ver
- EF Core 3.0 supported from 3.0.0 ver
- .Net 5 supported from 5.0.0 ver