@balena/node-metrics-gatherer/test/index.spec.ts

import { expect } from 'chai';
import 'mocha';

import { metrics } from '../src';

describe('MetricsGatherer', () => {
	beforeEach(() => {
		metrics.clear();
	});

	const expectToErr = (f: () => void) => {
		const errsBefore = metrics.internalErrorCount;
		f();
		expect(metrics.internalErrorCount - errsBefore).to.equal(1);
	};

	describe('Client Passthrough', () => {
		it('method on client should be accessible (check exponentialBuckets)`', () => {
			expect(metrics.client.exponentialBuckets(1, 2, 3)).to.eql([1, 2, 4]);
		});
	});

	describe('Error', () => {
		it('should fail if same name used for different kinds', () => {
			expectToErr(() => {
				metrics.counter('a_name', 1);
				metrics.histogram('a_name', 1);
			});
		});
	});

	describe('Gauge', () => {
		it('should create a gauge on inc() for undescribed metric', () => {
			metrics.inc('undescribed_gauge', 10);
			const output = metrics.output();
			expect(/TYPE undescribed_gauge gauge/.test(output)).to.be.true;
		});

		it('should not create a gauge, but a counter, if _total suffix found', () => {
			metrics.inc('build_error_total', 1);
			const output = metrics.output();
			expect(/TYPE build_error_total counter/.test(output)).to.be.true;
		});

		it('should inc and dec by 1 by default', () => {
			let output: string;

			metrics.inc('undescribed_gauge');
			output = metrics.output();
			expect(/undescribed_gauge 1/.test(output)).to.be.true;

			metrics.inc('undescribed_gauge');
			output = metrics.output();
			expect(/undescribed_gauge 2/.test(output)).to.be.true;

			metrics.dec('undescribed_gauge');
			output = metrics.output();
			expect(/undescribed_gauge 1/.test(output)).to.be.true;
		});
	});

	describe('Counter', () => {
		it('should create a counter', () => {
			metrics.describe.counter(
				'existent_counter',
				'a counter that should exist',
			);
			metrics.counter('existent_counter');
			const output = metrics.output();
			expect(/TYPE existent_counter counter/.test(output)).to.be.true;
		});

		it('should reset a counter', () => {
			metrics.describe.counter(
				'resetting_counter',
				'a counter that should be reset',
			);
			metrics.counter('resetting_counter');
			metrics.reset('resetting_counter');
			const output = metrics.output();
			expect(/resetting_counter 0/.test(output)).to.be.true;
		});

		it('should increment by 1 if not specified', () => {
			metrics.describe.counter('simple_counter', 'a simple counter');
			metrics.counter('simple_counter');
			const output = metrics.output();
			expect(/simple_counter 1/.test(output)).to.be.true;
		});

		it('should increment by a variable amount', () => {
			metrics.describe.counter(
				'variable_counter',
				'a counter that should increment by variable amounts',
			);
			metrics.counter('variable_counter', 1);
			metrics.inc('variable_counter', 3);
			const output = metrics.output();
			expect(/variable_counter 4/.test(output)).to.be.true;
		});

		it('should throw an error on dec() to counter', () => {
			expectToErr(() => {
				metrics.counter('counter_metric', 1);
				metrics.dec('counter_metric');
			});
		});
	});

	describe('Summary', () => {
		it('should throw an error on inc() to summary', () => {
			expectToErr(() => {
				metrics.summary('summary_metric', 1);
				metrics.inc('summary_metric');
			});
		});

		it('should throw an error on dec() to summary', () => {
			expectToErr(() => {
				metrics.summary('summary_metric', 1);
				metrics.dec('summary_metric');
			});
		});

		it('should allow single-line CustomParams', () => {
			const percentiles = [0.1, 0.5, 0.9];
			metrics.summary('summary_metric', 1, {}, { percentiles });
			expect(metrics.meta['summary_metric'].customParams.percentiles).to.eql(
				percentiles,
			);
		});
	});

	describe('Histogram', () => {
		it('should throw an error on inc() to histogram', () => {
			expectToErr(() => {
				metrics.histogram('histogram_metric', 1);
				metrics.inc('histogram_metric');
			});
		});

		it('should throw an error on dec() to histogram', () => {
			expectToErr(() => {
				metrics.histogram('histogram_metric', 1);
				metrics.dec('histogram_metric');
			});
		});

		it('should allow single-line CustomParams', () => {
			const buckets = [1, 9, 99, 999];
			metrics.histogram('histogram_metric', 1, {}, { buckets });
			expect(metrics.meta['histogram_metric'].customParams.buckets).to.eql(
				buckets,
			);
		});
	});
});