Dependency Injection Fundamentals Quiz Quiz

Explore key concepts, benefits, and practical scenarios involving dependency injection with this targeted quiz. Strengthen your understanding of dependency injection principles, design patterns, and their role in software development for maintainable, flexible code structures.

1. Core Principle of Dependency Injection

   Which main principle does dependency injection enforce by supplying required dependencies from outside a class rather than having the class create them directly?

   1. Hard Coding
   2. Separation of Concerns
   3. Inheritance
   4. Procedural Abstraction

   Explanation: Dependency injection supports the principle of separation of concerns because it keeps a class focused on its primary responsibility, while the management of dependencies remains outside. Hard coding refers to directly embedding values or logic, making code less flexible. Procedural abstraction is related to defining reusable operations but does not directly address dependency relationships. Inheritance is about class relationships and code reuse, not managing dependencies externally.

2. Common Benefits of Dependency Injection

   How does dependency injection improve unit testing in an application that uses external services, such as logging or data access?

   1. By combining multiple classes into one
   2. By allowing the injection of mock dependencies
   3. By optimizing runtime performance automatically
   4. By removing the need for interfaces

   Explanation: Dependency injection makes it easy to substitute real dependencies with mock or fake ones during unit tests, resulting in better isolated and controlled test scenarios. Combining multiple classes into one increases complexity and reduces testability. Removing the need for interfaces is not accurate; interfaces are often used in dependency injection for abstraction. Optimizing runtime performance is not a direct benefit of dependency injection.

3. Constructor Injection Scenario

   Given a class that needs an instance of an email sender to function, which dependency injection method provides the email sender through the class's constructor?

   1. Property Injection
   2. Static Reference
   3. Constructor Injection
   4. Singleton Injection

   Explanation: Constructor injection provides required dependencies through the class constructor at the time of object creation. Property injection uses public properties or setters instead of constructors. Singleton injection is not a standard term and could lead to lifetime management confusion. Static references do not involve injection; they are direct accesses and limit flexibility.

4. Identifying a Dependency

   In the context of dependency injection, which element is considered a dependency that can be injected into a class managing user accounts?

   1. A hardcoded string value for a username
   2. A data repository handling user data storage
   3. A conditional if-else statement in a function
   4. Loop iteration variables used in a method

   Explanation: A data repository is an external service the user account class relies on, making it a prime candidate for dependency injection. A hardcoded string value is just a value, not a service or component. Loop iteration variables are temporary and internal to the method's logic. Conditional statements control flow and are unrelated to dependencies.

5. Constructor Injection Drawback

   What is a potential drawback of using constructor injection when a class requires many dependencies, such as in a large reporting module?

   1. It forces all dependencies to use singleton lifetimes
   2. Constructor method can become too complex with too many parameters
   3. It always increases code duplication
   4. It eliminates the need for class abstraction

   Explanation: Injecting many dependencies through a constructor can lead to constructors with excessive parameters, reducing readability and maintainability. It does not inherently increase code duplication, which relates to repeating logic. Constructor injection does not force singleton lifetimes; lifetimes are managed separately. The need for class abstraction is not eliminated by using constructor injection.