How can I use an Excel file as test data correctly?

Question

How can I best use an Excel file as input for an xUnit test? Note that I do not want to use the data inside the Excel, but the Excel itself.

Let's say I have a UnitTests project, where I want to place some Excel files, that I need to put in my tests:

[Fact]
public void Constructor_ShouldReadExcelFile()
{
    var mapping = new ExcelMapping("excelfiles/test1.xlsx");

    Assert.True(mapping.Valid);
}

but, when running that, the CurrentWorkingDirectory is set to the bin\Debug\net7.0 dir, and I need to make a relative path:

[Fact]
public void Constructor_ShouldReadExcelFile()
{
    var mapping = new ExcelMapping("../../../excelfiles/test1.xlsx");

    Assert.True(mapping.Valid);
}

This will work, but is this the "right" way?

Answer 1

Your solution looks fine to me.

I often need to retrieve test data files for unit tests and generally proceed as follows. The test data are also under version control but in a different folder than the unit tests. In my unit test class, I define a relative path for the test data and make a member for the absolute path:

        const string testDataRelativePath = @"..\..\..\..\excelfiles\";
        string testDataFolderAbsolutePath;

The relative path is relative to the project folder where the unit test dll is output.

In the constructor of the test class I define a value for the absolute path.

using System.IO;
using System.Reflection;

    public class MyTestClass
    {
        public MyTestClass()
        {
            string projectDir = getProjectDir();
            testDataFolderAbsolutePath = Path.GetFullPath(Path.Combine(projectDir, testDataRelativePath));
        }

        internal static string getProjectDir()
        {
            Assembly assembly = Assembly.GetExecutingAssembly();
            return directoryPathNameFromAssemblyCodeBase(assembly);
        }

        internal static string directoryPathNameFromAssemblyCodeBase(Assembly assembly)
        {
            Uri codeBaseUrl = new Uri(assembly.CodeBase);
            string codeBasePath = Uri.UnescapeDataString(codeBaseUrl.AbsolutePath);
            return Path.GetDirectoryName(codeBasePath);
        }
    
        // ... Tests ...
    }

In the test itself, I then do something like this:

string excelFilePath = Path.Combine(testDataFolderAbsolutePath, "test1.xlsx");

I find that this gives better results on the plurality of systems on which the tests are running.