🐹 ✅ add test case for empty cache dir

The test covers the new case when an empty cache directory is
provided and a new cache file is created.

$ go test -v ./internal/cachedirectory -test.run ^\QTestUseProvidedEmptyCacheDirectory\E$
testing: warning: no tests to run
PASS
ok      github.com/github/codeql-action-sync/internal/cachedirectory    0.932s [no tests to run]

Author: marcellodesales

internal/cachedirectory/cachedirectory_test.go

@@ -89,6 +89,18 @@ func TestCreateCacheDirectoryWithTrailingSlash(t *testing.T) {
 	require.NoError(t, err)
 }
 
+func TestUseProvidedEmptyCacheDirectory(t *testing.T) {
+	temporaryDirectory := test.CreateTemporaryDirectory(t)
+	cacheDirectoryPath := path.Join(temporaryDirectory, "cache")
+	err := os.MkdirAll(cacheDirectoryPath, 0755)
+	require.NoError(t, err)
+	cacheDirectory := NewCacheDirectory(cacheDirectoryPath)
+	err = cacheDirectory.CheckOrCreateVersionFile(true, aVersion)
+	require.NoError(t, err)
+	cacheVersionFilePath := cacheDirectory.versionFilePath()
+	require.FileExists(t, cacheVersionFilePath)
+}
+
 func TestLocking(t *testing.T) {
 	temporaryDirectory := test.CreateTemporaryDirectory(t)
 	cacheDirectory := NewCacheDirectory(path.Join(temporaryDirectory, "cache"))