testing-patterns

MetaMask Connect Testing Patterns

Provider Mocking

• Mock the EIP-1193 provider's request method for unit tests
• Create a mock provider factory that returns controlled responses
• Example: const mockProvider = { request: vi.fn(), on: vi.fn(), removeListener: vi.fn() }
• Mock different responses for different methods (eth_accounts, eth_chainId, etc.)

Client Mocking

• Mock createEVMClient to return a controlled client object
• Mock client.connect(), client.disconnect(), client.getProvider(), client.switchChain()
• For multichain: mock createMultichainClient, client.invokeMethod(), client.on()

Singleton Cleanup

• createMultichainClient is a singleton — tests that create clients will share state
• Clear or reset the singleton between test runs
• Use beforeEach/afterEach to ensure clean state

Test Networks

• Use Sepolia (0xaa36a7) for E2E tests, never mainnet
• For Solana E2E: use devnet — supported in the MetaMask browser extension (mobile supports mainnet only)
• Mock RPC responses for unit tests; use real RPCs only for integration tests

Async Client Initialization

• createEVMClient and createMultichainClient are async — tests must await them
• In React testing, await the client before rendering components that depend on it
• Use act() wrapper for React state updates triggered by SDK events

Error Simulation

• Test user rejection: throw { code: 4001, message: 'User rejected' }
• Test pending connection: throw { code: -32002, message: 'Already pending' }
• Test network errors: simulate RPC failures
• Test disconnect scenarios

Event Testing

• Test that components react to accountsChanged, chainChanged events
• Simulate events by calling the mock provider's event handlers
• Test display_uri event handling for headless mode

Solana Testing

• Mock wallet-standard wallet object
• Mock signMessage, signAndSendTransaction features
• Test wallet discovery with mocked wallet registry