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@cofhe/hardhat-plugin extends Hardhat with everything you need to build and test FHE-enabled contracts locally: mock contracts, a pre-configured CoFHE client, and test utilities.

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What the plugin provides

  • Mock contracts deployed automatically on every npx hardhat test / npx hardhat node run, simulating the full CoFHE coprocessor stack on the Hardhat network.
  • hre.cofhe: a namespaced API for creating and connecting CoFHE clients with Hardhat signers.
  • hre.cofhe.mocks: utilities for reading raw plaintext values and interacting with mock contracts directly in tests.
  • Pre-configured networks: localcofhe, eth-sepolia, and arb-sepolia are injected automatically.

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Installation

1

Install the package

2

Import in your Hardhat config

hardhat.config.ts
That’s it. The plugin automatically deploys the mock contracts before every test run.

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Configuration

The plugin adds an optional cofhe key to your Hardhat config:
hardhat.config.ts
mocksDeployVerbosity controls how much output the plugin prints while deploying the mock contracts at the start of each npx hardhat test / npx hardhat node run: This is separate from runtime FHE-op logging, the entries printed when your tests actually call FHE.*. That is controlled onchain rather than from this config; see Logging.

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Pre-configured networks

The following networks are injected automatically. You can override any of them by defining the same key under networks in your config. For testnets, set PRIVATE_KEY (and optionally SEPOLIA_RPC_URL / ARBITRUM_SEPOLIA_RPC_URL) in your environment.

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Auto-deployment

Mock contracts are deployed automatically before:
  • npx hardhat test
  • npx hardhat node
To skip auto-deployment (e.g., when running tests only against an external RPC):

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Next steps

  • Client: create and connect a CoFHE client in tests.
  • Mock Contracts: read plaintext values and interact with mock contracts.
  • Logging: inspect FHE operations in test output.
  • Testing: end-to-end test patterns.