Monitor cache saves and add basic caching report

- Restore `CachingReport` instance in 'post' action
- Record keys for any entries saved
- Report caching activity as JSON in post action

__tests__/cache-utils.test.ts

@@ -1,5 +1,4 @@
 import * as cacheUtils from '../src/cache-utils'
-import * as path from 'path'
 
 describe('cacheUtils-utils', () => {
     describe('can hash', () => {
@@ -18,4 +17,97 @@ describe('cacheUtils-utils', () => {
             expect(posixHash).toBe(windowsHash)
         })
     })
+    describe('caching report', () => {
+        describe('reports not fully restored', () => {
+            it('with one requested entry report', async () => {
+                const report = new cacheUtils.CachingReport()
+                report.entryReport('foo').markRequested('1', ['2'])
+                report.entryReport('bar').markRequested('3').markRestored('4')
+                expect(report.fullyRestored).toBe(false)
+            })
+        })
+        describe('reports fully restored', () => {
+            it('when empty', async () => {
+                const report = new cacheUtils.CachingReport()
+                expect(report.fullyRestored).toBe(true)
+            })
+            it('with empty entry reports', async () => {
+                const report = new cacheUtils.CachingReport()
+                report.entryReport('foo')
+                report.entryReport('bar')
+                expect(report.fullyRestored).toBe(true)
+            })
+            it('with restored entry report', async () => {
+                const report = new cacheUtils.CachingReport()
+                report.entryReport('bar').markRequested('3').markRestored('4')
+                expect(report.fullyRestored).toBe(true)
+            })
+            it('with multiple restored entry reportss', async () => {
+                const report = new cacheUtils.CachingReport()
+                report.entryReport('foo').markRestored('4')
+                report.entryReport('bar').markRequested('3').markRestored('4')
+                expect(report.fullyRestored).toBe(true)
+            })
+        })
+        describe('can be stringified and rehydrated', () => {
+            it('when empty', async () => {
+                const report = new cacheUtils.CachingReport()
+
+                const stringRep = report.stringify()
+                const reportClone: cacheUtils.CachingReport = cacheUtils.CachingReport.rehydrate(stringRep)
+
+                expect(reportClone.cacheEntryReports).toEqual([])
+
+                // Can call methods on rehydrated
+                expect(reportClone.entryReport('foo')).toBeInstanceOf(cacheUtils.CacheEntryReport)
+            })
+            it('with entry reports', async () => {
+                const report = new cacheUtils.CachingReport()
+                report.entryReport('foo')
+                report.entryReport('bar')
+                report.entryReport('baz')
+
+                const stringRep = report.stringify()
+                const reportClone: cacheUtils.CachingReport = cacheUtils.CachingReport.rehydrate(stringRep)
+
+                expect(reportClone.cacheEntryReports.length).toBe(3)
+                expect(reportClone.cacheEntryReports[0].entryName).toBe('foo')
+                expect(reportClone.cacheEntryReports[1].entryName).toBe('bar')
+                expect(reportClone.cacheEntryReports[2].entryName).toBe('baz')
+
+                expect(reportClone.entryReport('foo')).toBe(reportClone.cacheEntryReports[0])
+            })
+            it('with rehydrated entry report', async () => {
+                const report = new cacheUtils.CachingReport()
+                const entryReport = report.entryReport('foo')
+                entryReport.markRequested('1', ['2', '3'])
+                entryReport.markSaved('4')
+
+                const stringRep = report.stringify()
+                const reportClone: cacheUtils.CachingReport = cacheUtils.CachingReport.rehydrate(stringRep)
+                const entryClone = reportClone.entryReport('foo')
+
+                expect(entryClone.requestedKey).toBe('1')
+                expect(entryClone.requestedRestoreKeys).toEqual(['2', '3'])
+                expect(entryClone.savedKey).toBe('4')
+            })
+            it('with live entry report', async () => {
+                const report = new cacheUtils.CachingReport()
+                const entryReport = report.entryReport('foo')
+                entryReport.markRequested('1', ['2', '3'])
+
+                const stringRep = report.stringify()
+                const reportClone: cacheUtils.CachingReport = cacheUtils.CachingReport.rehydrate(stringRep)
+                const entryClone = reportClone.entryReport('foo')
+
+                // Check type and call method on rehydrated entry report
+                expect(entryClone).toBeInstanceOf(cacheUtils.CacheEntryReport)
+                entryClone.markSaved('4')
+
+                expect(entryClone.requestedKey).toBe('1')
+                expect(entryClone.requestedRestoreKeys).toEqual(['2', '3'])
+                expect(entryClone.savedKey).toBe('4')
+            })
+        })
+    })
 })