How do you simulate external dependencies in software testing?

1 What are external dependencies?

External dependencies are any components or resources that your software depends on to function properly, but that are not part of your software itself. For example, your software may need to connect to a database to store or retrieve data, or to an API to access some functionality or information. External dependencies can also include hardware devices, network connections, or user inputs.

2 Why simulate external dependencies?

Simulating external dependencies in software testing can offer several advantages, such as isolating your software from the variability of real dependencies, controlling the inputs and outputs of your software, and reducing the cost and complexity of setting up and maintaining real dependencies. This allows you to test different scenarios and edge cases that may not occur in real dependencies, such as invalid data, unexpected responses, or timeouts. Simulating external dependencies can help ensure that your software is behaving correctly without the unpredictability or errors of real dependencies.

3 How to simulate external dependencies?

Software testing often requires simulating external dependencies, and there are various techniques and tools available depending on the type and level of simulation needed. Stubbing, for instance, is the simplest form of simulation, where a dependency is replaced with a predefined response or value that does not change. Mocking is a more advanced form of simulation, where a dependency is replaced with a simulated object that can mimic its behavior and interactions. Lastly, virtualizing is the most realistic form of simulation, where a virtual environment replicating the characteristics and functionality of real dependencies is created. Stubbing is useful for testing basic functionality, mocking for testing logic and behavior, and virtualizing for testing performance and reliability; however, each method requires different levels of effort and expertise.

4 When to simulate external dependencies?

When deciding whether or not to simulate external dependencies in software testing, there are several factors to consider. The availability and accessibility of real dependencies may influence the decision; if they are scarce, expensive, or unreliable, simulating them may be beneficial. Additionally, the scope and purpose of the testing should be taken into account; if you are testing the functionality or behavior of your software in isolation, simulating external dependencies may be preferable. Finally, the type and level of simulation needed should be assessed; if it is a simple or partial simulation such as stubbing or mocking, it can likely be managed with minimal effort and cost. However, if a complex or complete simulation such as virtualizing is required, more challenges and risks may arise in creating and maintaining it.

5 How to choose the right tools for simulation?

When it comes to simulating external dependencies in software testing, there are a variety of tools and frameworks available, depending on the programming language, platform, and technology you use. Popular options include Mockito (a mocking framework for Java), WireMock (a stubbing and mocking tool for HTTP-based APIs), and Docker (a virtualization platform). When selecting the right tool for simulation, it is important to consider the compatibility and integration with your software and testing environment, the functionality and flexibility for simulation, as well as the quality and reliability of the tool. The tools should support the languages, frameworks, and protocols you use, provide features and options for simulation, be well-designed and documented with good feedback from users, and not introduce any errors or side effects.

6 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?