Similar to this for Java: How can I make my JUnit tests run in random order?
And opposite to this for .Net: http://blogs.msdn.com/b/slange/archive/2010/06/02/ordering-method-execution-of-a-coded-ui-test.aspx
My reason is the same as in the first link - I wish to uncover any dependencies between the tests by shuffling the order every time they run.
Can this be done? I have to use MSTest because my tests drive GUI - they use Coded UI.
Since this hasn't been answered, I'll take a stab at it.
I don't know if the testing framework has this built in, but I would just code it myself. The simplest way might be to write a test method that calls all of the other test methods in a random order. You can be completely creative in the way you do this, you'll just want to set Playback.PlaybackSettings.ContinueOnError to true so the overall test doesn't fail when a single test fails.
I needed something similar so this may give you or anyone else a head start. You can just drop this in as it's own test class and it will automatically run every other unit test method in the same assembly a single time in a random order spanning unit test classes.
using System;
using System.Reflection;
using System.Collections.Generic;
using System.Linq;
using Microsoft.VisualStudio.TestTools.UnitTesting;
namespace Company.UnitTests
{
[TestClass]
public class RandomizerTest
{
private class TestClassProxy
{
public object Instance { get; set; }
public Type Type { get; set; }
public Action ClassCleanup { get; set; }
public Action<TestContext> ClassInitialize { get; set; }
public Action TestCleanup { get; set; }
public Action TestInitialize { get; set; }
public List<Action> TestMethods { get; set; }
}
[TestMethod]
public void TestRandom()
{
// ARRANGE
// attributes we'll be using to build our proxies (change these for NInject, other UT frameworks)
var classInitializeAttributeType = typeof (ClassInitializeAttribute);
var classCleanupAttributeType = typeof (ClassCleanupAttribute);
var testInitializeAttributeType = typeof (TestInitializeAttribute);
var testCleanupAttributeType = typeof (TestCleanupAttribute);
var testMethodAttributeType = typeof (TestMethodAttribute);
var proxies = (
from type in Assembly.GetExecutingAssembly().GetTypes()
where
type != typeof (RandomizerTest) && // don't include this class (infinite-loop)
type.GetCustomAttributes(typeof (TestClassAttribute), false).Length > 0 // only classes attributed with [TestClass]
let methods = type.GetMethods() // keep the methods for re-use
let instance = Activator.CreateInstance(type)
select new TestClassProxy
{
Type = type,
Instance = instance,
ClassInitialize = // select and wrap the method invokes inside an Action for re-use
methods
.Where(λ =>
λ.GetCustomAttributes(classInitializeAttributeType, false).Any())
.Select(λ => (Action<TestContext>) (tc => λ.Invoke(instance, new object[] { tc })))
.FirstOrDefault() ?? delegate { },
ClassCleanup =
methods
.Where(λ =>
λ.GetCustomAttributes(classCleanupAttributeType, false).Any())
.Select(λ => (Action) (() => λ.Invoke(instance, null)))
.FirstOrDefault() ?? delegate { },
TestInitialize =
methods
.Where(λ =>
λ.GetCustomAttributes(testInitializeAttributeType, false).Any())
.Select(λ => (Action) (() => λ.Invoke(instance, null)))
.FirstOrDefault() ?? delegate { },
TestCleanup =
methods
.Where(λ =>
λ.GetCustomAttributes(testCleanupAttributeType, false).Any())
.Select(λ => (Action) (() => λ.Invoke(instance, null)))
.FirstOrDefault() ?? delegate { },
TestMethods =
methods
.Where(λ =>
λ.GetCustomAttributes(testMethodAttributeType, false).Any())
.Select(λ => (Action) (() => λ.Invoke(instance, null))).ToList(),
}).ToList();
var random = new Random();
// ACT
// Note that the following may not work depending on how you developed your unit tests.
// If they're sharing state in any way (SQL DB, etc.) this may not be what you want.
// If that's the case alter the code below to only randomly sample test methods inside each class
// so that you can isolate tests per test class.
// This methodology assumes the cardinal rule: All unit tests are atomic. (given their proper setup/teardown)
// Plus if you're testing in a random order this is likely what you're after anyway.
// initialize all classes
foreach (var testClassProxy in proxies)
{
testClassProxy.ClassInitialize(null);
}
// run all test methods in a random order spanning all test classes until we run out
while (proxies.Count > 0)
{
// get random test class proxy
var proxy = proxies[random.Next(0, proxies.Count)];
// get random test method from proxy
var testMethod = proxy.TestMethods[random.Next(0, proxy.TestMethods.Count)];
// run test initialize
proxy.TestInitialize();
// run test method
testMethod(); // (ASSERT)
// run test cleanup
proxy.TestCleanup();
// remove test method from processing
proxy.TestMethods.Remove(testMethod);
// still have methods?
if (proxy.TestMethods.Count > 0)
{
continue;
}
// no, run class cleanup routine
proxy.ClassCleanup();
// remove the proxy from processing
proxies.Remove(proxy);
}
}
}
}
