Attraction is the surest test of a magnetism.

Explanation

**Step-by-Step Solution:**

1. **Understanding Magnetism:**
- Magnetism is a property of certain materials that allows them to attract or repel other magnetic materials. The most common magnets have two poles: a North Pole and a South Pole.

2. **Attraction as a Test:**
- The statement "Attraction is the surest test of magnetism" means that if a magnet attracts a material, it is likely that the material is magnetic. This is because magnets have the ability to pull magnetic materials towards them.

3. **Interaction with Magnetic Materials:**
- When a magnet is brought close to a magnetic material, it will attract the material regardless of whether the North or South Pole of the magnet is facing it. This shows that the material is magnetic.

4. **Repulsion as a Stronger Test:**
- However, if you bring two magnets close to each other, and they repel each other, this indicates that both objects are indeed magnets. For example, if the South Pole of one magnet is brought near the South Pole of another magnet, they will repel each other. This repulsion confirms that both objects are magnets and have like poles facing each other.

5. **Conclusion:**
- Therefore, while attraction indicates that a material is magnetic, repulsion is a stronger and more definitive test of magnetism, as it confirms that both objects are magnets with like poles.