Tests Flashcards
Difference between unit and UI tests
A unit test verifies the behavior of small part of the application, isolated from the environment and other parts, and is quite easy to implement, while an integration test covers interactions between different components, in the close-to-real-life environment, and requires more effort, including additional setup and teardown phases.
What makes a good unit test?
Easy to write. Developers typically write lots of unit tests to cover different cases and aspects of the application’s behavior, so it should be easy to code all of those test routines without enormous effort.
Readable. The intent of a unit test should be clear. A good unit test tells a story about some behavioral aspect of our application, so it should be easy to understand which scenario is being tested and — if the test fails — easy to detect how to address the problem. With a good unit test, we can fix a bug without actually debugging the code!
Reliable. Unit tests should fail only if there’s a bug in the system under test. That seems pretty obvious, but programmers often run into an issue when their tests fail even when no bugs were introduced. For example, tests may pass when running one-by-one, but fail when running the whole test suite, or pass on our development machine and fail on the continuous integration server. These situations are indicative of a design flaw. Good unit tests should be reproducible and independent from external factors such as the environment or running order.
Fast. Developers write unit tests so they can repeatedly run them and check that no bugs have been introduced. If unit tests are slow, developers are more likely to skip running them on their own machines. One slow test won’t make a significant difference; add one thousand more and we’re surely stuck waiting for a while. Slow unit tests may also indicate that either the system under test, or the test itself, interacts with external systems, making it environment-dependent.
Truly unit, not integration. Unit and integration tests have different purposes. Both the unit test and the system under test should not access the network resources, databases, file system, etc., to eliminate the influence of external factors.
What is the key of inversion of control?
The key point of IoC is to separate decision-making code (when to do something) from action code (what to do when something happens). This technique increases flexibility, makes our code more modular, and reduces coupling between components.
What is pure function?
In computer programming, a pure function is a function that has the following properties:
- Its return value is the same for the same arguments (no variation with local static variables, non-local variables, mutable reference arguments or input streams from I/O devices).
- Its evaluation has no side effects (no mutation of local static variables, non-local variables, mutable reference arguments or I/O streams).
Why static properties and fields can lead to problem with testing?
Static properties and fields or, simply put, global state, can complicate code comprehension and testability, by hiding the information required for a method to get its job done, by introducing non-determinism, or by promoting extensive usage of side effects. Functions that read or modify mutable global state are inherently impure.
Is using Singletons is a bad practice in term of testing?
Using Singletons is a bad practice that can (and should) be avoided in most cases; however, it is important to distinguish between Singleton as a design pattern, and a single instance of an object. In the latter case, the responsibility of creating and maintaining a single instance lies with the application itself. Typically, this is handed with a factory or Dependency Injection container, which creates a single instance somewhere near the “top” of the application (i.e., closer to an application entry point) and then passes it to every object that needs it. This approach is absolutely correct, from both testability and API quality perspectives
What is unit testing?
Unit testing is a method that instantiates a small part of our code and verifies its behavior independently from other parts of the project.
How to do unit testing and what does it entail?
A unit test typically features three different phases: Arrange, Act, and Assert (sometimes referred to as AAA). For a unit test to be successful, the resulting behavior in all three phases must be in line with expectations.
What is integration testing?
Integration testing focuses on testing and observing different software modules as a group. It is typically performed after unit testing is complete and precedes validation testing.
Benefits of unit testing
- Unit tests help to fix bugs early in the development cycle and save costs.
- It helps the developers to understand the testing code base and enables them to make changes quickly
- Good unit tests serve as project documentation
- Unit tests help with code re-use. Migrate both your code and your tests to your new project. Tweak the code until the tests run again.
What is the rule for testing LiveData?
To test LiveData it’s recommended you do two things:
Use InstantTaskExecutorRule
Ensure LiveData observation
InstantTaskExecutorRule runs all Architecture Components-related background jobs in the same thread so that the test results happen synchronously, and in a repeatable order. When you write tests that include testing LiveData, use this rule!
