Merge pull request #2366 from balena-os/using-infer-steps-lock-unit-test

Add unit test for usingInferStepsLock

src/device-state/index.ts

@@ -268,9 +268,11 @@ function emitAsync<T extends keyof DeviceStateEvents>(
 
 const inferStepsLock = () =>
 	takeGlobalLockRW('inferSteps').disposer((release) => release());
-function usingInferStepsLock<T extends () => any, U extends ReturnType<T>>(
+// Exported for unit test
-	fn: T,
+export function usingInferStepsLock<
-): Bluebird<UnwrappedPromise<U>> {
+	T extends () => any,
+	U extends ReturnType<T>,
+>(fn: T): Bluebird<UnwrappedPromise<U>> {
 	return Bluebird.using(inferStepsLock, () => fn());
 }
 

test/unit/device-state.spec.ts

@@ -0,0 +1,30 @@
+import { expect } from 'chai';
+import * as deviceState from '~/src/device-state';
+
+describe('usingInferStepsLock', () => {
+	it('should not allow to start a function call without finishing the previous sequential call of the function', async () => {
+		const result: string[] = [];
+		const fn = async (id: number, str: string) => {
+			return deviceState.usingInferStepsLock(async () => {
+				if (id < 3 || id === 20) {
+					result.push(`Started ${id}, ${str} call`);
+					await fn(id + 1, 'first');
+					await fn(id + 1, 'second');
+					result.push(`Finished ${id}, ${str} call`);
+				}
+			});
+		};
+		await fn(1, 'master');
+		await fn(20, 'master');
+		expect(result).to.deep.equal([
+			'Started 1, master call',
+			'Started 2, first call',
+			'Finished 2, first call',
+			'Started 2, second call',
+			'Finished 2, second call',
+			'Finished 1, master call',
+			'Started 20, master call',
+			'Finished 20, master call',
+		]);
+	});
+});