import { computeDelta } from '../src/billing/stripe';

describe('computeDelta', () => {
  it('returns the difference when billable exceeds prior', () => {
    expect(computeDelta(800, 500)).toBe(300);
  });

  it('returns 0 when billable equals prior', () => {
    expect(computeDelta(500, 500)).toBe(0);
  });

  it('never returns a negative value when billable is below prior', () => {
    expect(computeDelta(300, 500)).toBe(0);
  });

  it('returns the full billable amount when nothing was reported before', () => {
    expect(computeDelta(500, 0)).toBe(500);
  });
});