So-called dry-tab test kits are widely available. They consist of a test tube or vial along with a chemical reagent in tablet form, packed individually in foil. Kept in its packaging the chemicals should remain in good condition for a couple of years. Tablets don't always dissolve well, so often a special crusher is included.

Powders are easier to dissolve, but more difficult to measure precisely and to handle without spillage.

Liquid reagents get around these problems, often providing a quicker result, but they have a shorter shelf life.

Alternatively for complete ease, there are pH dip meters - pocket meters that you can simply dip in the pond for an instant reading.