23 May 2011

Data driven test in NUnit with csv source data

I wanted to test a date parser across a large range of values so wanted a simple test harness to test all the values.

The test framework options around c# / .net seem to be:
  • MSTest - can do csv via jet, but can't do inline test data which is something I also want.
  • NUnit - can do inline data driven test data (with the TestCase(data...) attribute), and has support for extending this via the TestCaseSource attribute.
  • xUnit - confusing (aka flexible), doesn't seem to get me to my end result any faster after a bit of searching around.
I've used NUnit and combined TestCaseSource with a simple wrapper class around the csv parsing library

To get this to work:
  • Save your csv file in your test project
  • add the file to your project (in visual studio 2008 in this case)
  • right-click on the csv file in solution explorer, click properties, change "Copy to Output Directory" to "Copy Always"
  • download the binaries (dlls) for csv reader from code project, add a reference to this in your test project
  • add a private method to your test class for reading the csv file and returning an enumarable (see code below)
  • add the TestCaseSource attribute to your test method(s) that you want to use the csv data, referencing your new IEnumerable method (see code below)


using System.Collections.Generic;
using System.IO;
using LumenWorks.Framework.IO.Csv;
using NUnit.Framework;

namespace mytests
{
    class MegaTests
    {
        [Test, TestCaseSource("GetTestData")]
        public void MyExample_Test(int data1, int data2, int expectedOutput)
        {
            var methodOutput = MethodUnderTest(data2, data1);
            Assert.AreEqual(expectedOutput, methodOutput, string.Format("Method failed for data1: {0}, data2: {1}", data1, data2));
        }

        private int MethodUnderTest(int data2, int data1)
        {
            return 42; //todo: real implementation
        }

        private IEnumerable<int[]> GetTestData()
        {
            using (var csv = new CsvReader(new StreamReader("test-data.csv"), true))
            {
                while (csv.ReadNextRecord())
                {
                    int data1 = int.Parse(csv[0]);
                    int data2 = int.Parse(csv[1]);
                    int expectedOutput = int.Parse(csv[2]);
                    yield return new[] { data1, data2, expectedOutput };
                }
            }
        }
    }
}


references:

1 comment:

static hiss said...

I had no idea nUnit supported this and I'v used it for years.

Thanks for this post, was able to adapt it suit my problem perfectly