Add unit test to ensure journalctl process is spawned with expected

arguments.

Signed-off-by: Ivan <ivan@mish.guru>

test/26-journald.spec.ts

@@ -0,0 +1,57 @@
+import { SinonStub, stub } from 'sinon';
+import constants = require('../src/lib/constants');
+import { spawnJournalctl } from '../src/lib/journald';
+import { expect } from './lib/chai-config';
+
+describe('journald', () => {
+	let spawn: SinonStub;
+
+	beforeEach(done => {
+		spawn = stub(require('child_process'), 'spawn');
+		done();
+	});
+
+	afterEach(done => {
+		spawn.restore();
+		done();
+	});
+
+	it('spawnJournalctl calls spawn child process with expected args', () => {
+		spawnJournalctl({
+			all: true,
+			follow: true,
+			count: 10,
+			unit: 'nginx.service',
+			containerId: 'abc123',
+			format: 'json-pretty',
+		});
+
+		const expectedCommand = `chroot`;
+		const expectedCoreArgs = [`${constants.rootMountPoint}`, 'journalctl'];
+		const expectedOptionalArgs = [
+			'-a',
+			'--follow',
+			'-u',
+			'nginx.service',
+			'-t',
+			'abc123',
+			'-n',
+			'10',
+			'-o',
+			'json-pretty',
+		];
+
+		const actualCommand = spawn.firstCall.args[0];
+		const actualCoreArgs = spawn.firstCall.args[1].slice(0, 2);
+		const actualOptionalArgs = spawn.firstCall.args[1].slice(2);
+
+		expect(spawn.calledOnce).to.be.true;
+
+		expect(actualCommand).deep.equal(expectedCommand);
+		expect(actualCoreArgs).deep.equal(expectedCoreArgs);
+
+		expectedOptionalArgs.forEach(arg => {
+			expect(actualOptionalArgs).to.include(arg);
+		});
+	});
+});