.Net core testing with Xunit

Question

This is the first time I am writing test case and I am not sort of stuck and not sure how to proceed further.

I have the following API. In the below sample I have 2 endp

Answer 1

An expression tree may not contain a call or invocation that uses optional arguments

You are trying to "call" a method ScanAsync on not already set up GetContext(). To solve this you have to Setup return value for GetContext() before you tried to Setup ScanAsync()

---

This code is very hard to test so let's refactor it.

You have to change direct calls of _clientAccessor.GetContext() to injection of IDynamoDBContext. DynamoDbClientInitialization doesn't make sense as can be easily replaced with IAmazonDynamoDb. To get rid of verbose config reading code lines, use

services.AddAWSService<IAmazonDynamoDB>();

All calls to DynamoDb should be encapsulated on a separated class called, for example, DynamoDbManager

public class DynamoDbManager<T> : DynamoDBContext, IDynamoDbManager<T> where T : class
    {
        private DynamoDBOperationConfig _config;

        public DynamoDbManager(IAmazonDynamoDB client, string tableName): base(client)
        {
            _config = new DynamoDBOperationConfig()
            {
                OverrideTableName = tableName
            };
        }

        public Task<List<T>> GetAsync(IEnumerable<ScanCondition> conditions)
        {
            return ScanAsync<T>(conditions, _config).GetRemainingAsync();
        }

        public Task SaveAsync(T item)
        {
            return base.SaveAsync(item, _config);
        }
    }

Now your controller will be changed in this way ValuesController

public class ValuesController : Controller
    {
        private readonly IDynamoDbManager<MyModel> _dynamoDbManager;
        //This interface is used to setup dynamo db and connection to aws
        private static string dynamoDbTable = string.Empty;

        public ValuesController(IOptions<Dictionary<string, string>> appSettings, IDynamoDbManager<MyModel> dynamoDbManager)
        {
            _dynamoDbManager = dynamoDbManager;
            var vals = appSettings.Value;
            dynamoDbTable = vals["dynamoDbTable"];
        }

        [HttpGet("api/data")]
        public async Task<IActionResult> GetAllData(string type, string status)
        {
            var conditions = new List<ScanCondition>
            {
                new ScanCondition("Type", ScanOperator.Equal, type),
                new ScanCondition("Status", ScanOperator.Equal, status)
            };
            var result = await _dynamoDbManager.GetAsync(conditions);
            var response = result.Select(_ => _.UpdatedBy.ToLower()).ToList();
            return Ok(response);
        }

        [HttpPost("api/save")]
        public async Task<IActionResult> SaveData([FromBody] List<MyModel> listData, string input, string name, string type)
        {
            foreach (var data in listData)
            {
                //populating data here
                await _dynamoDbManager.SaveAsync(data);
            }
            return Ok();
        }
    }

Refactoring is finished, start writing unit tests ValuesControllerTests

public class ValuesControllerTests
    {
        private Mock<IDynamoDbManager<MyModel>> _dbManager;
        private ValuesController _valuesController;

        public ValuesControllerTests()
        {
            var mockRepository = new MockRepository(MockBehavior.Loose);
            _dbManager = mockRepository.Create<IDynamoDbManager<MyModel>>();
            var options = new OptionsWrapper<Dictionary<string, string>>(new Dictionary<string, string>()
            {
                {"dynamoDbTable", nameof(MyModel) }
            });
            _valuesController = new ValuesController(options, _dbManager.Object);

        }

        [Fact]
        public async Task GetAllData_ShouldSelectUpdateByInLowerCase()
        {
            //
            var searchResult = new List<MyModel>()
            {
                new MyModel() {UpdatedBy = "UpdatedBy1"}
            };
            _dbManager
                .Setup(_ => _.GetAsync(It.Is<List<ScanCondition>>(list => list.Count == 2)))
                .ReturnsAsync(searchResult);

            //

            var result = await _valuesController.GetAllData("typeValue", "statusValue");

            //
            var okResult = result as OkObjectResult;
            Assert.NotNull(okResult);
            var values = okResult.Value as List<string>;
            Assert.Contains("updatedby1", values);
        }

        [Fact]
        public async Task SaveData_ShouldCallSaveForAllRequestedData()
        {
            //
            var listData = new List<MyModel>()
            {
                new MyModel(),
                new MyModel(),
                new MyModel()
            };
            _dbManager
                .Setup(_ => _.SaveAsync(It.IsAny<MyModel>()))
                .Returns(Task.CompletedTask);

            //

            var result = await _valuesController.SaveData(listData, "","", "");

            //
            _dbManager.Verify(_ => _.SaveAsync(It.IsAny<MyModel>()), Times.Exactly(3));
        }
    }

That's all, I did two tests for each controller action because its far more understandable - if you realy need only one test you can easily join them