How can I mock IDistributedLockProvider method AcquireLockAsync in XUnit Unit Test? about distributedlock

[grahamauty]

Thanks @madelson, you've pointed me in the right direction. I have the following which now gives me a working unit test:

    private readonly Mock<IDistributedLockProvider> _mockDistributedLockProvider;
    ....
    public SutComponentTests() {
        _mockDistributedLockProvider = new Mock<IDistributedLockProvider>();
        _sut = new SutComponent(_mockDistributedLockProvider.Object);
    }

    [Fact]
    public async Task TestMethod() {
       _mockDistributedLockProvider.Setup(r => r.CreateLock(
                It.IsAny<string>()))
            .Returns(new MockDistributedLock());

        var result = await _sut.MethodUnderTest();

        // Assert ...
    }

where MockDistributedLock is defined as:

    internal class MockDistributedLock : IDistributedLock {
        public string Name => throw new NotImplementedException();

        public IDistributedSynchronizationHandle Acquire(TimeSpan? timeout = null, CancellationToken cancellationToken = default) {
            throw new NotImplementedException();
        }

        public ValueTask<IDistributedSynchronizationHandle> AcquireAsync(TimeSpan? timeout = null, CancellationToken cancellationToken = default) {
            // THE IMPORTANT BIT
            return new ValueTask<IDistributedSynchronizationHandle>();
        }

        public IDistributedSynchronizationHandle TryAcquire(TimeSpan timeout = default, CancellationToken cancellationToken = default) {
            throw new NotImplementedException();
        }

        public ValueTask<IDistributedSynchronizationHandle> TryAcquireAsync(TimeSpan timeout = default, CancellationToken cancellationToken = default) {
            throw new NotImplementedException();
        }
    }

[madelson]

In the future if we implement #38, this might become even easier; you could use an in-memory lock as a fairly-realistic mock.

[madelson]

@grahamauty yep you can't mock the extension directly. However, the extension is just 2 calls: CreateLock + AcquireAsync. So, you can just mock CreateLock() to return a lock whose AcquireAsync method does what you'd want it to do. Does that make sense?