a7d79c4e3f4a407ee937749b3fc1db29 by 2025

Author:2025
Language: eng
Format: epub

Chapter 4 Unit test .net appliCations

Figure 4-1. The datatable.json file Build Action and Copy to Output Directory directives

We need now to write a little helper in C#, named EmbeddedJsonFileHelper, based on Newtonsoft.Json to read the file and fill a DataTable as shown in Listing 4-7.

Listing 4-7. The EmbeddedJsonFileHelper class

using Newtonsoft.Json;

namespace Apress.UnitTests.DataTables.Helpers;

public static class EmbeddedJsonFileHelper

{

public static T GetContent<T>(string filename)

{

return JsonConvert.DeserializeObject<T>(File.ReadAll

Text($"{filename}.json"));

}

}

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Chapter 4 Unit test .net appliCations

We are ready to write our unit test! Listing 4-8 shows the Order ServiceTests test class with its test method named GetAsync_WhenGet AsyncRepositoryMethodReturnAFilledDataTable_GetAsyncServiceMethod ReturnsAListOfTransactions.

Listing 4-8. The OrderServiceTests class

using Apress.UnitTests.DataTables;

using Apress.UnitTests.DataTables.Helpers;

using ExpectedObjects;

using NSubstitute;

using System.Data;

using Xunit;

namespace Apress.UnitTests;

public class OrderServiceTests

{

[Fact]

public async Task GetAsync_WhenGetAsyncRepository

MethodReturnAFilledDataTable_GetAsyncServiceMethod

ReturnsAListOfTransactions()

{

// Arrange

IOrderRepository orderRepositoryMock = Substitute.

For<IOrderRepository>();

DataTable table = new DataTable();

table.Columns.Add("Id", typeof(long));

table.Columns.Add("Quantity", typeof(int));

table.Columns.Add("Date", typeof(DateTime));

var datatable = EmbeddedJsonFileHelper.GetContent

<DataTable>(@"DataTables\datatable");

foreach (DataRow row in datatable.Rows)

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Chapter 4 Unit test .net appliCations

{

table.ImportRow(row);

}

orderRepositoryMock.GetAsync().Returns(x => table);

var expectedResult = new List<Order>

{

new Order { Id = 1, Quantity = 10, Date = DateTime.

Parse("2025-01-20") },

new Order { Id = 2, Quantity = 20, Date = DateTime.

Parse("2025-02-12")},

new Order { Id = 3, Quantity = 30, Date = DateTime.

Parse("2025-02-02")}

}.ToExpectedObject();

// Act

var service = new OrderService(orderRepositoryMock);

var result = await service.GetAsync();

// Assert

expectedResult.ShouldEqual(result);

}

}

As you can see, I have reused the libraries I introduced in the previous chapter. Additionally, using JSON to mock a DataTable greatly improved the test efficiency and readability! However, I had to create a DataTable manually with only the columns. Why? When using Newtonsoft.Json to deserialize JSON into a DataTable, integer numbers are often converted into long instead of int. This behavior occurs because Newtonsoft.Json uses the most inclusive numeric type (long) by default to avoid data loss from large numbers. Same for decimal, it’s using doubles instead of 84

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