This company cofounder lived with her first employee for 3 weeks before hiring him to make sure he was a good fit

It's so important that Kruustük lived with her first employee for three weeks before she took him on following a few Skype interviews.

"I felt a good connection to this guy but couldn't hire someone I'd never met," Kruustük said.

Testilo was born four and a half years ago out of how testers were being treated in the industry. She wanted to build a platform which would appreciate the work they do.

"I became very frustrated because my time as a tester wasn't appreciated," she told Business Insider. "Testers were always competing with each other — when really it was always supposed to be everyone's responsibility."

Along with her boyfriend-turned-husband Marko, she entered the world's largest hackathon, Angelhack, and took home first place, winning $25,000 in investment to launch Testlio. Now, the company has 200 freelance testers from 40 countries, covering 65 languages. Their customers include Microsoft, Lyft, Salesforce, CBS, Strava, NBA and Hotels.com.

Although Testlio has grown, some things have not changed — particularly the culture of the company, which remains important to Kruustük.

"The idea of Testlio has been the same since the beginning," Kruustük said. "The heart is the testers and the community. We pay our testers on an hourly basis, and we've built the platform to let the testers work together."

As a first time founder, Kruustük naturally came up against some difficulties and challenges.

This is what she learned from becoming an entrepreneur.

1. Learning takes time.

Kruustük said she learns from her own experience, rather than learning from others, which is a time-consuming process.

"I haven't built this confidence and I'm constantly second guessing myself," she said. "Sometimes making decisions takes a longer time — because I have to go through everything on my own."

However, doing things this way means she has learned a lot, and has also realised that making mistakes is actually fine, even though it has taken her a few years to gain that attitude.

"I tried to give myself the mindset of 'I am doing the best I can every day to the best of my abilities,'" said Kruustük. "I can't look back into the past and think 'What was all of that that went wrong' — if something doesn't work out its fine, we'll learn from it — next time we'll do it better... but it's hard to get there."

2. You develop a thicker skin.

At the beginning, Kruustük says she took everything personally. She said she even cried on Marko's shoulder a few times when receiving feedback on the company. She said she finds it difficult not to look at other founders and think they all seem to have everything worked out.

"I have a lot thicker skin now, but its been a rollercoaster for me," Kruustük said. "Luckily over time I've tried to take myself out of this rollercoaster and really think about the business sense."

Kruustük says her husband has played a big part in teaching her to be tougher. In a Medium post, Kruustük wrote about how he bought her a horse — Rockerfeller — when they got married. Little did she know her new pet would help break her stress cycle and mentally and physically take some time out from the business. Somehow, Marko knew Rockerfeller was just what she needed.

Marko had previous business experience, and Kruustük says he taught her how to not emotionally attach to every single thing that happened.

"When I look at my cofounder, he's so strong," she said. "Then I look at myself — he's trying to get me more on the ground. It's very easy to get stuck into the nitty gritty details, instead of focusing on the long term goal, and learning to take emotions out of it."

3. Diversity is key.

Half of all Testlio's employees are women or from minority groups. 40% of the leadership are also women. For Kruustük, it was important that she created an environment that was welcoming to everyone.

The employees also come from a range of different backgrounds, speaking 10 different foreign languages.

4. Every employee should add to the culture.

Company culture is vital for Kruustük. She and Marko still interview everyone they add to the team, but they tend to ask the candidates about their hobbies, rather than their technical abilities.

"Building a great company culture helps spread good word about the company," she said. "We always talk about how diverse we are, and how everyone is welcome here — that's really important as well."

However, they're also very selective. Kruustük said the company only accepts 3-4% of the testers that apply, because they have to keep the quality very high. This is why they insist on meeting everyone personally before offering them a job.

In fact, Kruustük lived with her first employee, Meelik Gornoi, for four weeks before she took him on. Both cofounders knew they liked him — he had just left Skype as one of their first employees, and was looking for something new to try — but they had only interviewed him on video chats.

"I felt a good connection to this guy but couldn't hire someone I'd never met," Kruustük said. "We had a call and I asked: 'Can you come to Austin, Texas for the next three weeks? We can get to know you and you can get to know us — if you're quitting Skype after 10 years, you want to make sure you make the right decision."

He accepted the offer, and was given the job as soon as it became clear he was a good fit.

5. Always keep pushing yourself.

If Kruustük could go back to when she was first starting up Testlio and give herself some advice, it would be to keep pushing your limits.

"You have to put yourself into uncomfortable positions because that's the only way you can grow," she said. "I wish I could have someone on my shoulder saying 'It'll be okay,' and [telling me] to keep pushing. There's pain and there's failure, but that's the only way you grow."