I plan on planting some citrus this spring. My soil is mainly rock, gravel and sand with some (perhaps 10%) organic matter. Drainage is quite good as you'd imagine. Should I amend the soil in any way prior to planting? Should I test the ph levels as well?

Cheers, Barrie.

What else are you growing in that soil, ie weeds, vegetables, other fruit trees etc. Are they doing well or not ?
Soil testing would be good if you wanted to choose rootstocks that perform best in your soil, but if you already have the plants, or are buying Citrus on common nursery stocks, or planting own seedlings, you will need to cater for all.

pH is important in the way it governs the availability( not the ammount in the soil ) of required plant nutrients. Generally between about pH 5.5 and 7 in soils, nutrients are available to plants, even if present in low ammounts, and/ or restricted for uptake when present in high ammounts.
At lower pH some become highly available, causing toxicity. At higher pH others get locked up causing deficiency, even if present in good ammounts.

For container media, which are not soils, they usually have a much higher organic matter content than soils, ie 50% pine bark, 40% coir etc.
The upper limit of pH is about 6.5 in relation to nutrient availiability.

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If your drainage is good, it probably will not matter much one way or the other. The pH would be a bigger consideration.