In a previous post, I discussed Parameter Value Coverage (PVC). One of the easiest ways to add PVC to your test suite is to use Row Tests, sometimes called Parameterized Tests. Row test is the idea of writing a single unit test, but passing many different values in.

Different testing frameworks implement row tests differently.

MsTest uses an attribute called DataResourceAttribute. This supports anything from a csv, Excel file or xml, to a full-blown database.

For a single Unit Test, NUnit’s Row tests are far superior. However, for a larger test project, you will see that DataSourceAttribute with external data sources, scales nicely and compares to NUnits TestCaseSource. However, it is not as easy to get it right the first time. It needs a step by step tutorial.

Step 1 – Create a the Project

1. In Visual Studio click File | New | Project.
2. Select Unit Test Project for C#.
3. Give it a name and a path and click OK.

Step 2 – Add a csv file

1. Create a folder in your visual studio project called Data.
2. Right-click on the data folder and choose Add | New Item.
3. Create new text file named: Data.csv
4. Add the following to the csv.

Value1, Value2, ExpectedMinValue, Message
1,10, 1, 1 is less th an 10.
192, 134, 134, 134 is less than 192.
101, 99, 99, 99 is less than 101.
77, 108, 77, 77 is less than 108.
45, 37, 37, 37 is less than 34.
12, 18, 12, 12 is less than 18.

Step 3 – Save the CSV file with the correct encoding

Note: The CSV file needs to be saved with an encoding that doesn’t add junk characters.

1. Click File | Advanced Save Options.
2. Choose this Encoding option: Unicode (UTF-8 without signature) – Codepage 65001
3. Click OK and then click save.

Note: VS 2017 doesn’t have an Advance Save Options menu item.

1. Click File | Save Data.csv as.
2. Click the drop down on the Save button and choose Save with Encoding.
3. Choose this Encoding option: Unicode (UTF-8 without signature) – Codepage 65001
4. Click OK and then click save.

Step 4 – Set CSV File Properties

The CSV file needs to be copied on build.

1. Right-click on the CSV file and choose Properties.
2. Change the Copy to output directory to: Copy if newer

Step 5 – Add a Unit Test method

Note: We won’t have a real project to test. We will just test Math.Min() for an example.

1. Add a reference to System.Data.
2. Add the TestContext property. (See line 9 below)
3. Add a DataSource attribute to the test method. (See line 12 below)
4. Use TestContext.DataRow[0] to get the first column. (See line 16 below)
   Note: You can also access the column by the column name we used: TestContext.DataRow[Value1]

5. Assign variables for the rest of the columns. (See lines 16-19 below)
6. Add the test and the assert. (See lines 22 and 25)

using System;
using Microsoft.VisualStudio.TestTools.UnitTesting;

namespace MsTestRowTestExample
{
    [TestClass]
    public class UnitTest1
    {
        public TestContext TestContext { get; set; }

        [TestMethod]
        [DataSource("Microsoft.VisualStudio.TestTools.DataSource.CSV", @"Data\Data.csv", "Data#csv", DataAccessMethod.Sequential)]
        public void TestMethod1()
        {
            // Arrange
            int a = Convert.ToInt32(TestContext.DataRow[0]);
            int b = Convert.ToInt32(TestContext.DataRow[1]);
            int expected = Convert.ToInt32(TestContext.DataRow[2]);
            string message = TestContext.DataRow[3].ToString();

            // Act
            var actual = Math.Min(a, b);

            // Assert
            Assert.AreEqual(expected, actual, message);
        }
    }
}

You finished! Good job!.

Use Common Csv files for Parameter Value Coverage

While this method involved way more steps than anything with NUnit to set up, tt can actually be a bit quicker for subsequent tests and quite useful when testing larger projects. Once you have the csv files setup, you can reuse them for many methods. For example, for every method that takes a string, you could use the same DataSource to get Parameter Value Coverage (PVC).

null, A null string
"", An empty string, String.Empty, or ""
" ", One or more spaces " "
"	", One or more tabs "	"
"
", A new line or Environment.NewLine
"Hello, world!", A valid string.
"&*^I#UYLdk1-KNnS1.,Dv0Hhfwelfnzsdase", An invalid or junk string
গঘ, Double-byte Unicode characters