sinonjs/sinon

Features

• Mocking Frameworks - Serves as a comprehensive framework for creating simulated objects and stubbing method calls.
• Controlled Interface Fakes - Allows replacing function implementations to return specific values or trigger errors for controlled testing.
• Test Double Implementations - Implements a comprehensive set of spies, stubs, and mocks to replace real dependencies.
• Argument Constraint Matchers - Provides logic for validating function call arguments against custom predicates and constraints during assertions.
• Method Interception Proxies - Uses dynamic proxy systems to wrap original methods and record metadata or control return values.
• Test-Time - Returns specific values, throws errors, or resolves promises by overriding existing functions.
• Interaction Verification Utilities - Enables recording and asserting that object methods are called with expected arguments and in the correct order.
• Fake Timers - Trigger timeouts and intervals instantly by replacing the system clock with a fake timer to avoid waiting for real time.
• Function Call Tracking - Maintains an internal ledger of arguments, contexts, and return values for every invocation of a wrapped function.
• Function Behavior Replacement - Simulates specific dependencies by intercepting function calls and returning predefined values or throwing errors.
• Test Isolation - Prevents test leakage by grouping multiple fakes into a sandbox that restores the original state.
• Global Object Interception - Implements the replacement of native JavaScript clock and timer functions to simulate time progression.
• Mocking and Spying Libraries - Provides a full toolkit of spies, stubs, and mocks for isolation and interaction tracking.
• Object Interaction Verification - Checks that specific methods on an object are called with expected arguments and in the correct order.
• Dependency Mocking - Replaces module dependencies and network calls with controlled substitutes to simulate specific behaviors.
• Timer Mocks - Allows overriding native timers to control time-based execution and trigger timeouts instantly.
• Test Sandbox Restoration - Ships a sandbox mechanism that tracks all modified properties and restores original behavior via a single cleanup call.
• Test Spying Utilities - Tracks function call arguments, return values, and invocation counts to verify object interactions.
• Virtual Time Testing - Simulates the passage of time by overriding the system clock to trigger timers without waiting in real-time.
• Accessor Stubbing - Controls or monitors access to specific properties by replacing getters and setters on objects.
• Fake Timer Utilities - Offers a specialized library to override the system clock for instant timeout and interval triggering.
• Mock Expectation Definitions - Provides syntax for defining anticipated method calls and return sequences on mock objects.
• API Request Mocking - Mocks server responses and inspects outgoing requests by simulating a network environment.
• Test State Sandboxes - Includes a sandbox mechanism to group fakes and automatically restore original behavior between tests.
• Instance-Level Stubbing - Replaces every method in a constructor instance with a stub to simulate a full object.
• Instance Stubbing - Provides the ability to intercept object instantiation and automatically stub every method of the resulting instance.
• Unit Testing - Provides the essential tooling for isolating units of code and verifying their logic in JavaScript.
• Testing and Quality Assurance - Test spies, stubs, and mocks for JavaScript.
• Testing Frameworks - Mocking library with spies, stubs, and mocks.

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