Testing in the demo, traders can find out if the broker is good or not to invest. However, new traders, most of the time lose money due to knowledge rather than a broker. People often lose more than they earn. That’s why most brokers like Eurotrader offer traders free educational courses. This broker also offers mt4 & mt5 trading platforms with no additional charge during withdrawal.
I always test all my new strategies, ideas and occasionally EA I've found on demo first. I'm not risking my life account.
Making a strategy is easy, but executing a strategy is a completely different story. Traders will probably feel different after spending weeks, months, and many times losing real money, watching their account balances shrink. So, it is better to improvise or adjust your strategy continuously according to changing market. Demo practice is the best way to improve your trading strategy. Forex broker like TP Global FX offers a free demo account.