A few days ago Microsoft has finally announced that some of the old(er) windows phones would soon get the new shiny OS. That left a few windows phone owners a little disappointed. I remember that only a few months ago it was clear that all (or at least most) windows phone devices would be updated to Windows 10 and now it seems that they would in fact keep running windows 8.1.

As the proud owner of one Lumia 925 – I feel a little cheated, but not surprised. I have used the insider builds of the latest and greatest for a few weeks, and while I enjoyed using the new OS it was not “production ready” just yet.Nokia-Lumia-925-smartphone-Black-update-jpg

This is not the first time I’ve tried the insider builds – about a year ago when I just got my phone I immediately installed the newest version I could get my hands on – and then removed it after less than 4 hours (and 3 failed attempts). I was buggy, crashed all the time and basic capabilities (a.k.a calling other people) would not work.

This time around the new version worked better, I got most of the functionality (call app still crashed though) and I liked what I saw and was ready for the next version that would crash the bugs I kept on reporting – which today I know would likely not happen.

Part of being in the insider program was that my phone kept asking me if I’m happy with the current experience and whether I would recommend this particular build to a friend. I would answer that I am happy but a few glitches still preventing me from telling someone else to try it out. My aim was to provide feedback so that the things that bothered me the most would be addressed. Another tings I learnt since is that Microsoft was also using this feedback to decide which devices would get the new OS and which would be left out.

Don’t get me wrong – I think that from a business perspective this is a good path to go. The next version of Windows mobile should be released and decreasing the scope and/or supported devices is one way to do so.

There is another aspect to this decision: One thing I cared about for all of the phones I owned in the past (I tend to break them – a lot) is that no matter the OS I wanted it to get updated.

I want the latest and greatest – even with an older phone. In the past I bought Nexus 4 phone because at the time it that was the only Android phone that consistently got updated and for the same reason I got my latest phone as well. As a user I hate the practice of some vendors – which don’t bother to update the phones firmware just because it’s not economically viable – or is it?

I had some work in the Windows phone 8, then UWP (Universal Windows platform) 8.1 and 10 space. And decision like this that make me a bit worried.

I worked for a company that made an investment and created a windows 8 app. Before we managed to complete it – there came //build announcing that the way to go from now on is to write Universal apps (8.1). We made an effort and managed to convert most of the code to the new platform, and we were waiting for some crucial functionality when the next //Build came along and kindly explained that the old Universal Apps (a.k.a 8.1) were over and there’s a new platform now. At that point the managers got a little worried.

It seemed that every year there’s a change and the new shine we were working on was now obsolete. I guess we were lucky we haven’t started a year before working on Windows 7 apps (remember those)…

I love my phone – it works amazingly, has a good battery life and I love the user experience (tiles!) but when I’m asked about it I feel the need to apologize – because there are not a lot of applications for it. As a developer I completely understand why – companies don’t want to invest in new platform and by the time it seems stable enough – it gets replaced. The low market share of Windows phones doesn’t help either, but users won’t buy a phones that don’t have their favorite app – do you see the magic cycle yet?

The next //Build conference starts this Wednesday – and as a software developer and (a proud) Windows phone owner I’m both excited and worried. I want to learn about the new, cool stuff but I fear that just like the last time I would also learn which technologies are going to kick the bucket.

Nokia-Lumia-925-front-png Until then – Happy coding…

Comparing Two objects using Assert.AreEqual()

4 comments

Monday, March 21, 2016

Anyone who ever googled (binged?) about unit testing have heard about the “one assert per test rule”. The idea is that every unit test should have only one reason to fail. It’s a good rule that help me write good, robust unit test – but like all such rules-of-the-thumb it’s not always right (just most of the time).
If you’ve been using unit tests for some time you might have come to a conclusion that using multiple asserts is not always a bad idea – in fact for some tests it’s the only way to go…
Consider the following class:
public class SomeClass
{
    public int MyInt { get; set; }
    public string MyString { get; set; }
}
And now imagine a test in which that SomeClass is the result of your unit tests – what assert would you write?
[TestMethod]
public void CompareTwoAsserts()
{
    var actual = new SomeClass { MyInt = 1, MyString = "str-1" };

    Assert.AreEqual(1, actual.MyInt);
    Assert.AreEqual("str-1", actual.MyString);
}
Using two asserts would work, at least for a time. The problem is that failing the first assert would cause an exception to be thrown leaving us with no idea if the second would have passed or failed.
We can solve this issue by splitting the test into two tests – one test per assert. Which seems like an overkill in this case - we’re not asserting for two different, unrelated “things”, we’re in fact testing one SomeClass that happen to have two properties.
Ideally I would have liked to write the following test:
[TestMethod]
public void CompareTwoObjects()
{
    var actual = new SomeClass {MyInt = 1,MyString = "str-1"};
    var expected = new SomeClass {MyInt = 1,MyString = "str-1"};

    Assert.AreEqual(expected, actual);
}
Unfortunately it would fail. The reason is that deep down inside our assert have no idea what is an “equal” object and so it runs Object.Equals and throws an exception in case of failure. Since the default behavior of Equals is to compare references (in case of classes) the result is a fail.
Due to this behavior there are many (myself included) who suggest overriding Equals to make sure that the actual values are compared. which could be a problem if our production code cannot be changed just to accommodate our tests.  There are ways around this limitation – such as using a Helper class (ahem) that would do the heavy lifting by inheriting (or not) the original class and adding custom Equals code.
I propose another option – one that could be useful , especially when there’s a need to compare different properties in different tests.

Using Fake objects to compare real objects

In order to change the way two objects are compared in an assert we only need change the behavior of one of them – the expect value (might change depending on unit testing framework). And who is better in changing behavior of objects in tests than your friendly-neighborhood mocking framework.
And so using FakeItEasy I was able to created the following code:
[TestMethod]
public void CompareOnePropertyInTwoObjects()
{
    var actual = new SomeClass { MyInt = 1, MyString = "str-1" };
    var expected = new SomeClass { MyInt = 1, MyString = "str-1" };

    var fakeExpected = A.Fake<someclass>(o => o.Wrapping(expected));

    A.CallTo(() => fakeExpected.Equals(A<object>._)).ReturnsLazily(
        call =>
        {
            var other = call.GetArgument<someclass>(0);

            return expected.MyInt == other.MyInt;
        });

    Assert.AreEqual(fakeExpected, actual);
}
What we got here is a new fake object a.k.a fakeExpected which would call custom code when its Equals method is called.
The new Equals would return true if MyInt is the same in the two objects. I’ve also create the new fake using Wrapping  so that the original methods on the class would still be called – I really care about ToString which I would override to produce meaningful assertion message.
Now all I needed to so is to compare the fakeExpected with the actual result from the test.
In a similar way I’ve created a new extension method that would compare the properties on two classes:
public static T ByProperties<T>(this T expected)
{
    var fakeExpected = A.Fake<T>(o => o.Wrapping(expected));

    var properties = expected.GetType().GetProperties(BindingFlags.Instance | BindingFlags.Public);

    A.CallTo(() => fakeExpected.Equals(A<object>._)).ReturnsLazily(
        call =>
        {
            var actual = call.GetArgument<object>(0);

            if (ReferenceEquals(null, actual))
                return false;
            if (ReferenceEquals(expected, actual))
                return true;
            if (actual.GetType() != expected.GetType())
                return false;

            return AreEqualByProperties(expected, actual, properties);
        });

    return fakeExpected;
}

private static bool AreEqualByProperties(object expected, object actual, PropertyInfo[] properties)
{
    foreach (var propertyInfo in properties)
    {
        var expectedValue = propertyInfo.GetValue(expected);
        var actualValue = propertyInfo.GetValue(actual);

        if (expectedValue == null || actualValue == null)
        {
            if (expectedValue != null || actualValue != null)
            {
                return false;
            }
        }
        else if (typeof (System.Collections.IList).IsAssignableFrom(propertyInfo.PropertyType))
        {
            if (!AssertListsEquals((IList) expectedValue, (IList) actualValue))
            {
                return false;
            }   
        }
        else if (!expectedValue.Equals(actualValue))
        {
            return false;
        }
    }

    return true;
}

private static bool AssertListsEquals(IList expectedValue, IList actualValue)
{
    if (expectedValue.Count != actualValue.Count)
    {
        return false;
    }

    for (int I = 0; I < expectedValue.Count; I++)
    {
        if (!Equals(expectedValue[I], actualValue[I]))
        {
            return false;
        }
    }

    return true;
}
And now I can use the following to compare my expected value with the value returned by the test:
[TestMethod]
public void CompareTwoObjectsByProperties()
{
    var actual = new SomeClass { MyInt = 1, MyString = "str-1" };
    var expected = new SomeClass { MyInt = 1, MyString = "str-1" };

    Assert.AreEqual(expected.ByProperties(), actual);
}
Simple(ish) is it? I prefer this method since I no longer need to make changes to my production code (e.g. SomeClass) but I can still use plain vanilla unit testing framework.

What do you think?
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