Custom Jest Test For Clock Drift and Ranges

to-be-within-tolerance.spec.ts

// Define and declare a custom jest expectation so we can handle clock drift tolerances
declare global {
  // eslint-disable-next-line @typescript-eslint/no-namespace
  namespace jest {
    interface Matchers<R> {
      toBeWithinTolerance(center: number, tolerance: number): R;
    }
  }
}

expect.extend({
  toBeWithinTolerance(received: number, center: number, tolerance: number) {
    const floor = center - tolerance;
    const ceiling = center + tolerance;
    const pass = received >= floor && received <= ceiling;
    if (pass) {
      return {
        message: () => `expected ${received} not to be within tolerance range ${center}+/- ${tolerance} (${floor} - ${ceiling})`,
        pass: true,
      };
    } else {
      return {
        message: () => `expected ${received} to be within tolerance range ${center}+/- ${tolerance} (${floor} - ${ceiling})`,
        pass: false,
      };
    }
  },
});

describe('DynamoTokenStore custom jest expectation .toBeWithinTolerance()', () => {
  const center = 5;
  const tolerance = 2;
  const underflow = [0, 1, 2];
  const overflow = [8, 9, 10];
  const withinTolerance = [3, 4, 5, 6, 7];
  test.each(withinTolerance)(`should assert %p is within tolerance ${center}+/-${tolerance}`, (value) => {
    expect(value).toBeWithinTolerance(center, tolerance);
  });
  test.each(underflow)(`should assert underflow value %p is outside tolerance ${center}+/-${tolerance}`, (value) => {
    expect(value).not.toBeWithinTolerance(center, tolerance);
  });
  test.each(overflow)(`should assert overflow value %p is outside tolerance ${center}+/-${tolerance}`, (value) => {
    expect(value).not.toBeWithinTolerance(center, tolerance);
  });
});