Heat the oil in a large saucepan over medium-heat. Add sausage. Fry, stirring frequently, until the sausage is cooked through. Add garlic.
Add diced tomatoes. Season with salt and pepper. Bring the mixture to a simmer and reduce the heat to medium-low. Cover and continue simmering for about 15 minutes. Add basil at the end of cooking.
Meanwhile, bring a large pot of salted water to a boil. Add gnocchi to the boiling water and cook gnocchi according to the package instructions. Remember, gnocchi will float to the surface when finished cooking. Once finished, drain and toss with sauce in saucepan for about 2 minutes to coat.