it('validates a valid chain',()=>{
        blockchain2.addBlock('foo');
        // conventional method for check true and false is toBe
        expect(blockchain.isValidChain(blockchain2.chain)).toBe(true);
    });

    it('invalidates a chain with a corrupt the genesis block',()=>{
        blockchain2.chain[0].data = 'bad data';

        expect(blockchain.isValidChain(blockchain2.chain)).toBe(false);
    });

    it('invalidates a corrput chain',()=>{
        blockchain2.addBlock('foo');
        blockchain2.chain[1].data = 'not foo';

        expect(blockchain.isValidChain(blockchain2.chain)).toBe(false);
    });