How do lenders assess servicing for investment property loans in Australia?

I am looking at my first investment property purchase here in Australia and I am trying to understand how lenders assess servicing for investment property loans. Do they typically count all of the expected rental income, or do they apply a discount to it? I am also curious how existing personal debts factor into the serviceability calculation. Any insights on what buffers or assessment rates are common in 2026 would be really helpful.