We roll a cask-shaped roller over each mattress for 30,000 cycles to simulate approximately eight years of use. Then, comfort is assessed based on sleeping on your back and on your side. The higher the score, the closer the mattress will feel to how it did when you first got it.

Using an oscilloscope we measure the movement of the mattress after a standard impact (17.5kg). This test simulates a sleeping person's body turning. We also count how many bounces up and down the mattress shows before it stops moving. Higher-scoring mattresses show fewer bounces and less movement during standard impact.

We measure height and firmness when the mattress is brand new, then roll a cask-shaped roller over each one for 30,000 cycles to simulate eight years of use. We then note any differences between the out-of-the-box test and after the simulation. Mattresses with a higher score show fewer signs of sagging over time. Lower-scoring mattresses show more sagging over time. Mattresses with a higher score will generally feel the same as they did out of the box after eight years of use.

We test how much fluid a mattress takes in, to simulate how permeable it is to sweat over time. Lower-scoring mattresses take in more fluid. Fluid can cause damage and odour buildup over time.

We roll a cask-shaped roller over each mattress for 30,000 cycles to simulate approximately eight years of use. Visible damage such as cracking, broken springs or pilling contribute to a 'mattress fatigue' score. A higher score here means less damage.

Our priority is testing the mattresses you'll see in stores and major online retailers. To do this, we check current market data to see what's most popular. We ran a CHOICE member poll to determine which firmness we should test, and the majority of our members requested firm mattresses. We also test models that a lot of members have requested.

We test both retail and bed-in-a-box mattresses under the same conditions via partnerships with independent labs in Europe. These labs are equipped with precisely calibrated measurement tools and reference machines to test and compare products. Our test focuses on firmness, and if the mattress lives up to any other claims it makes. We're looking to find the brands that will keep you comfortable over the lifetime of the mattress.

Our expert test partners in Europe assess mattresses from all over the world all year round. Their labs are set up to exclusively test mattresses.

Unlike other product review sites, we don't accept free test models from manufacturers. This helps us remain independent, so we can review without any interference. We buy products anonymously from a variety of retailers, or direct from manufacturers, then bring them into our labs. We buy what you'd get, so you can be sure the model we test hasn't been 'tweaked' for better performance.

We send a new batch of mattresses to Europe every 12 months for testing.

While opinions about comfort can be subjective, a good mattress will retain its firmness over its lifetime. Our intensive lab test simulates around eight years of real-world mattress use. A good mattress should stay comfortable over its lifetime, not getting any less or more firm.