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diff --git a/src/physics/electricField.test.ts b/src/physics/electricField.test.ts
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+import { describe, expect, it } from 'vitest';
+import { electricField, COULOMB_CONSTANT } from './electricField';
+
+describe('Coulomb electric field', () => {
+  it('points away from a positive charge with inverse-square magnitude', () => {
+    const field = electricField({ x: 2, y: 0, z: 0 }, [{ x: 0, y: 0, z: 0, coulombs: 1e-9 }]);
+    expect(field.x).toBeCloseTo(COULOMB_CONSTANT * 1e-9 / 4);
+    expect(field.y).toBe(0);
+    expect(field.z).toBe(0);
+  });
+  it('superposes opposite charges in the same direction at the midpoint', () => {
+    const field = electricField({ x: 0, y: 0, z: 0 }, [
+      { x: -1, y: 0, z: 0, coulombs: 1e-9 },
+      { x: 1, y: 0, z: 0, coulombs: -1e-9 },
+    ]);
+    expect(field.x).toBeCloseTo(2 * COULOMB_CONSTANT * 1e-9);
+  });
+  it('omits singular samples within the visualization exclusion radius', () => {
+    expect(electricField({ x: 0, y: 0, z: 0 }, [{ x: 0, y: 0, z: 0, coulombs: 1e-9 }])).toEqual({ x: 0, y: 0, z: 0 });
+  });
+});