Have you ever purchased a product and discovered that you love it? Did that experience encourage you to return to the brand when possible? I discovered that I love a particular brand of scissors when my husband gave me a pair along with other quilt-related items. Made of titanium the scissors stay sharp (almost dangerous) and never rust or get old looking. I've had them for several years and they still shine, cut like a razor, and have not needed any adjustments. Of course no one touches my scissors. No one. Not even to cut fabric. These scissors haven't a clue that paper exists. So keeping them in great shape has been easy. These scissors are the best on the market. When I needed another pair to keep near the long-arm, I knew exactly which brand to purchase.
Does that testimonial have you wanting to know the brand? That's the point of providing a testimonial for a product. If you truly like a brand, telling readers why you like it helps them to make decisions when looking for similar products. Readers appreciate your opinion because you have already tested the brand.
By the same token, being honest about why you do not like a product also informs your readers. If I were to tell you that Mary's All Purpose Cleaner did not remove the lime buildup in my bathtub, you'd know that I hate it and will likely never buy it again. There are two problems with this statement: first, the product is treated badly and second, there are no specific reasons for the negative comments.
But what if I were to tell you I use the product, and I like but am not over-the-moon crazy about it? Would you be more likely to believe my testimonial? The best testimonials are believable. No one really only loves a product. And even when we dislike a product, chances are we don't only dislike it. We find ourselves somewhere in the middle: a product is good for X reasons and not-so-good for X reasons. A testimonial shows the reader where this product fits in the gauge of the best and the worst.
A testimonial about a product should present all of the information about that product. Readers need all of the information because they want to make their own decisions, albeit informed by your testimonial. Your job in writing a testimonial is to "open the box," meaning to provide all of the information that a reader may need to make an informed decision. In my first example above, I raved about the product, providing little information about why I loved it so much. The piece also is not specific: I've have the scissors for "several" years, and overly exaggerated: "No one ever touches them. They've never been used on paper." Too much exaggeration can be a clue that the piece is just a lovefest and not a true testimonial.
In the cleaner example, I said very little and all of it was negative. Anyone reading this example would have additional questions. What chemicals are in the product? How safe is it? Does it claim to kill germs? Is it made for the bathroom, kitchen and other places? How long has it been on the market? None of which are addressed.
Testimonials (from the word testament) means to tell the full truth. An easy way to do that is to remember the 5W1H strategy--who (brand); what (product and purpose); when (recommendation for future purchases); where/how (experience); and why (outcome). Another way of thinking about testimonial writing is that the reader should clearly know your opinion, know that your problem was solved, know your experience, and know whether you recommend the product.
Some great examples of product testimonials appear on HubSpot. Though I found several other examples, these were my favorite. In fact, while reading the Codecademy testimonials--there are videos, but I'm a reader--I found myself wanting to learn a little about computer code. The HubSpot site has nine examples of testimonials. While these are all good, your blog testimonial will be a little different. Still, you are telling a story and it's perfectly fine to write it that way.
Begin with the problem and explain it so that the reader can see herself in your shoes. Continue the story by telling how you found the product (who/what) its purpose and why you chose it. Now you can tell, truthfully, how well the product worked (where/how). What aspects did you like or dislike? State specifically whether you would recommend the product (when).
Your testimonial is complete, honest, believable, and helpful to readers. After writing a few testimonials, you may find that readers trust your opinions and may even come to you for help in choosing products in your niche--one very good reason to consider including testimonials in your writing.