React.js, often simply called React, is a highly popular JavaScript library for building user interfaces. Developed and maintained by Facebook, React is renowned for its component-based architecture and the ability to efficiently update and render components when data changes. It is a foundational tool for developing modern web and mobile applications, allowing developers to create dynamic and interactive user interfaces with ease. React's vast ecosystem, including tools like React Native for mobile app development, makes it a top choice for frontend development and a key player in the world of web technologies.
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Practice Test
161. What is the primary purpose of testing React applications?
A. To write documentation
B. To ensure that the app works as expected
C. To improve code readability
D. To create a user interface
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Answer: To ensure that the app works as expected
162. Which testing library is commonly used for unit testing React components?
A. Jest
B. React Testing Library
C. Enzyme
D. Mocha
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Answer: React Testing Library
163. In React, what is the role of a test runner?
A. It renders React components
B. It generates test reports
C. It executes test suites
D. It analyzes code coverage
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Answer: It executes test suites
164. What is a unit test in the context of React testing?
A. A test that verifies the entire application
B. A test that checks a single unit of code
C. A test that simulates user interactions
D. A test that checks for memory leaks
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Answer: A test that checks a single unit of code
165. Which testing library provides utilities for querying and interacting with React components in tests?
A. Jest
B. React Testing Library
C. Enzyme
D. Mocha
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Answer: React Testing Library
166. In React testing, what is the purpose of a "snapshot test"?
A. To take screenshots of the app
B. To capture the current component state
C. To compare the rendered output
D. To record user interactions
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Answer: To compare the rendered output
167. What does the term "mocking" refer to in React testing?
A. Simulating the behavior of dependencies
B. Creating fake components
C. Running tests concurrently
D. Generating random test data
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Answer: Simulating the behavior of dependencies
168. In React, what is the purpose of a "test suite"?
A. A collection of test cases
B. A folder containing test files
C. A group of related components
D. A set of test runners
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Answer: A collection of test cases
169. What is the recommended approach for structuring tests in a React application?
A. By organizing tests based on file structure
B. By using a single large test file
C. By writing tests within components
D. By using external test runners
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Answer: By organizing tests based on file structure
170. In React, what is a "test double" or "mock"?
A. A component that renders other components
B. A fake implementation of a dependency
C. A type of test suite
D. A test report
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Answer: A fake implementation of a dependency
