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contracts...MockRateProvider.sol

// SPDX-License-Identifier: GPL-3.0-or-later
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.

// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License
// along with this program.  If not, see <http://www.gnu.org/licenses/>.

pragma solidity ^0.7.0;

import "@balancer-labs/v2-interfaces/contracts/pool-utils/IRateProvider.sol";
import "@balancer-labs/v2-solidity-utils/contracts/math/FixedPoint.sol";
import "https://github.com/balancer-labs/balancer-v2-monorepo/blob/master/pkg/solidity-utils/contracts/openzeppelin/ERC20.sol";

contract MockRateProvider is IRateProvider {
    uint256 internal _rate;
    uint256 internal _virtualSupply;
    IERC20 internal _mainToken;

    constructor(IERC20 mainToken) {
        _rate = FixedPoint.ONE;
        _virtualSupply = 1000000 * 1e18;
        _mainToken = mainToken;
    }

    function getRate() external view override returns (uint256) {
        return _rate;
    }

    function mockRate(uint256 newRate) external {
        _rate = newRate;
    }

    function getVirtualSupply() external view returns (uint256) {
        return _virtualSupply;
    }

    function mockVirtualSupply(uint256 virtualSupply) external {
        _virtualSupply = virtualSupply;
    }

    function getMainToken() external view  returns (IERC20) {
        return _mainToken;
    }

    function mockMainToken(IERC20 mainToken) external {
        _mainToken = mainToken;
    }
}