In a large colander, strain and rinse chickpeas, black beans, and kidney beans and set aside.
In a small jar, combine the olive oil, mustard, honey, garlic, salt, and black pepper. Shake until emulsified and well combined. Set aside.
In a large bowl, combine the diced vegetables and beans, and give it a good stir to ensure everything is well combined.
Drizzle the salad with the dressing and toss again to ensure everything is well coated. Taste the salad and season with additional salt and pepper to taste.
The salad can be served immediately or stored in an airtight container in the fridge for up to 5 days.