SnowInsurance.sol

// SPDX-License-Identifier: GPL-3.0

pragma solidity >=0.7.0 <0.9.0;

contract StoreWeather {

    enum Weather { sunny, cloudy, rainy, snow }
    address public owner = msg.sender;
    Weather currentWeather;

    function store(Weather _setWeatherTo) public {
        require(msg.sender == owner, "Only the owner can do this!");
        currentWeather = _setWeatherTo;
    }

    function retrieve() public view returns (Weather){
        return currentWeather;
    }
}

contract SnowInsurance {
    address payable public insurer;
    address payable public insured;
    address public oracle;
    uint public premium;

    constructor(address _oracleAddress) {
        require(_oracleAddress != address(0));
        insurer = payable(msg.sender);
        oracle = _oracleAddress;    
    }

    function openContract(uint _premium) public payable {
        require (msg.sender == insurer, "Only insurer can open contract");
        require (msg.value > 0, "Must send ether to open contract");
        require (_premium > 0, "Must define premium greater than 0");
        premium = _premium;
    }
    
    function insureMe() public payable {
        require (address(this).balance > 0, "Contract not open yet");
        require (insured == address(0), "Contract already in use");
        require (msg.value >= premium, "Must pay premium");
        insured = payable(msg.sender);
        // check if there's change
        if ((msg.value - premium) > 0){
            insurer.transfer(msg.value - premium);
        }
    }

    function cancel() public {
        require (msg.sender == insurer, "Only insurer can cancel");
        insured.transfer(premium);
        insurer.transfer(address(this).balance);
    }
 
    function claim() public {
        require (msg.sender == insured, "Only insured can claim");

        StoreWeather sw = StoreWeather(oracle);
        require (sw.retrieve() == StoreWeather.Weather.snow);

        insurer.transfer(premium);
        insured.transfer(address(this).balance);
    }
}

improved a bit so it's easier to do TDD