Build local unit tests | Android Developers
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You can call Java code from Kotlin and vice-versa seamlessly. Both Kotlin and Java generate the same bytecode, so there's no fear that you're shipping something completely different with Kotlin. Start by writing some simple and small parts of your app in Kotlin as you start getting familiar with its constructs and syntax which, by the way, is super-simple. I started using Kotlin for small parts of a large project, including a few UI components and simple business logic.
Its interoperability is truly a blessing. No more NullPointerExceptions My team has been developing Android apps for three years, and NPE's have been one of the most common reasons for crashes in our apps. It is so nice to catch NPEs at compile time instead of crashing apps at runtime.
- Fundamentals of Testing
- Why you should use Kotlin for Android development
- Three Reasons Why We Should Not Use Inheritance In Our Tests
How does this work in practice? By default, all variables are non-null. Suppose you have a string variable and you are trying to assign a value to it: Now, try to do this: With this type system in place, it will be very difficult for NPEs to occur in your app at runtime. JetBrains specializes in creating some of the most used IDEs in the world. You can mix and match Kotlin and Java code in the same project, and everything still works great.
Fundamentals of Testing | Android Developers
And fewer lines of code means smaller file sizes for Kotlin, compared to Java equivalents. I have converted several Java files of differing sizes into Kotlin using the Android Studio plugin, and I have yet to find a case where the file size wasn't smaller after the conversion. Kotlin is way more readable too, once you understand its syntax. It's not verbose, like Java. It is crisp, concise, and reduces a lot of much of the boilerplate code that developers must write every day.
For instance, consider this click listener in Java. Everyone uses click listeners in their Android apps, but it takes a lot of code and ceremony in Java just to perform an action on the click of a button.
Kotlin is an enterprise language Kotlin is not the new kid in town. It's been around for a few years, although it wasn't production ready until JetBrains developed it for solving practical, real-world development problems. The traversal of the test class hierarchy is wasted CPU time. I learned this from a book titled Effective Unit Testing. For example, if this takes only 2 milliseconds per test case, and our test suite has tests, our test suite is 6 seconds slower than it could be.
That might not sound like a long time but it feels like eternity when we run our tests in our own computer. Also, the wasted CPU time is not the only thing that slows down our feedback loop. If we use inheritance in our test classes, we must pay a mental price as well. Tests document the way our code is working right now. Tests ensure that our code is working correctly.
We want to make our tests easy to read because If our tests are easy to read, it is easy to understand how our code works. If our tests are easy to read, it is easy to find the problem if a test fails.
I will demonstrate what I meant by using a simple example. The relevant part of the TodoCrudServiceImpl class looks as follows: After all, we have to write other tests after we have finished this one, and it makes sense to reuse as much code as possible.
First, we create the AbstractMockitoTest class. This class ensures that all test methods found from its subclasses are invoked by the MockitoJUnitRunner. Its source code looks as follows: This class provides useful utility methods and constants for other test classes which tests methods related to todo entries.
The source code of our test class looks as follows: Mock; import static org. The weirdest thing is that if we take only a quick look at it, it looks pretty clean.
However, when we take a closer look at it, we start asking the following questions: It seems that the TodoRepository is a mock object. This test must use the MockitoJUnitRunner.
Build local unit tests
Where the test runner is configured? Where can we find this method? The unit test found from this class uses constants. Where these constants are declared?
The unit test asserts the information of the returned Todo object by calling the assertTodo method. Nevertheless, finding out the answers to these questions takes time because we have to read the source code of the AbstractTodoTest and AbstractMockitoTest classes.
If we cannot understand a simple unit like this one by reading its source code, it is pretty clear that trying to understand more complex test cases is going to be very painful. A bigger problem is that code like this makes our feedback loop a lot longer than necessary.
We just learned three reasons why we should not use inheritance in our tests. The obvious question is: That is a very good question, and I will answer to it in a different blog post.