Rinse beans and place in a pot with 4 cups water, bring to the boil then lower heat and simmer for 60 minutes. Add more water to the pot if you find its drying up, cook until tender. Drain and set aside. Whilst the beans are cooking, prepare the rest of the ingredients for the salsa.
In a large bowl, mix together the cooked beans, tomatoes, red onion, corn, spring onions, olives and coriander. Then add the avocado (as the last ingredient) and gently toss again until well combined.
In a small bowl, whisk together the olive oil, red wine vinegar, garlic, cumin, salt and pepper. Pour over the salad and lightly toss again.
Chill in the fridge for 60 minutes for the flavours to develop and serve.