To spot a paid testimonial, look for the tags #ad, #sponsored or #partner under the video or the post. They mean a company paid for it.
The other signs:
A personal promo code at the end of the video.
A purchase link in the description.
A « miracle » story with no downside at all.
If you see these signs: the opinion may still be sincere, but it is not neutral. Look for a second source with no connection to the brand.
Limitation: in Canada, influencers must disclose their partnerships, but not all of them do.
To picture it: when someone is paid to speak well of a product, it is advertising, even when it looks like a friend’s advice.
Trusted links: Influencer marketing (Competition Bureau Canada)