Add a unit test for the cleanup module

__tests__/cleanup.test.ts

@@ -0,0 +1,15 @@
+import * as core from '@actions/core'
+
+import {run} from '../src/cleanup'
+
+describe('run', () => {
+  beforeEach(async () => {
+    jest.spyOn(core, 'error').mockImplementation(jest.fn())
+  })
+
+  test('it does not log any errors interacting with Docker by default', async () => {
+    await run()
+
+    expect(core.error).not.toHaveBeenCalled()
+  })
+})

src/cleanup.ts

@@ -1,11 +1,18 @@
 import * as core from '@actions/core'
 import Docker from 'dockerode'
 
-export async function run(): Promise<void> {
+// This method performs housekeeping checks to remove Docker artifacts
+// which were left behind by old versions of the action or any jobs
+// which may have crashed before deleting their own containers or networks
+//
+// cutoff - a Go duration string to pass to the Docker API's 'until' argument, default '24h'
+export async function run(cutoff = '24h'): Promise<void> {
   try {
     const docker = new Docker()
-    const untilFilter = JSON.stringify({until: '24h'})
+    const untilFilter = JSON.stringify({until: cutoff})
+    core.info(`Pruning networks older than ${cutoff}`)
     await docker.pruneNetworks({filters: untilFilter})
+    core.info(`Pruning containers older than ${cutoff}`)
     await docker.pruneContainers({filters: untilFilter})
   } catch (error) {
     core.error(`Error cleaning up: ${error.message}`)