Resource: increase code coverage

arduino/resources/helpers.go

@@ -52,6 +52,11 @@ func (r *DownloadResource) IsCached(downloadDir *paths.Path) (bool, error) {
 
 // Download a DownloadResource.
 func (r *DownloadResource) Download(downloadDir *paths.Path, config *downloader.Config) (*downloader.Downloader, error) {
+	path, err := r.ArchivePath(downloadDir)
+	if err != nil {
+		return nil, fmt.Errorf("getting archive path: %s", err)
+	}
+
 	cached, err := r.TestLocalArchiveIntegrity(downloadDir)
 	if err != nil {
 		return nil, fmt.Errorf("testing local archive integrity: %s", err)
@@ -61,11 +66,6 @@ func (r *DownloadResource) Download(downloadDir *paths.Path, config *downloader.
 		return nil, nil
 	}
 
-	path, err := r.ArchivePath(downloadDir)
-	if err != nil {
-		return nil, fmt.Errorf("getting archive path: %s", err)
-	}
-
 	if stats, err := path.Stat(); os.IsNotExist(err) {
 		// normal download
 	} else if err == nil && stats.Size() > r.Size {

arduino/resources/helpers_test.go

@@ -84,6 +84,29 @@ func TestResourcesSanityChecks(t *testing.T) {
 	}
 }
 
+func TestResourceErrorHandling(t *testing.T) {
+	tmp, err := paths.MkTempDir("", "")
+	require.NoError(t, err)
+	defer tmp.RemoveAll()
+
+	r := &DownloadResource{
+		ArchiveFileName: "..",
+		CachePath:       "cache",
+	}
+
+	c, err := r.IsCached(tmp)
+	require.Error(t, err)
+	require.False(t, c)
+
+	d, err := r.Download(tmp, nil)
+	require.Error(t, err)
+	require.Nil(t, d)
+
+	e, err := r.TestLocalArchiveIntegrity(tmp)
+	require.Error(t, err)
+	require.False(t, e)
+}
+
 func TestDownloadApplyUserAgentHeaderUsingConfig(t *testing.T) {
 	goldUserAgentValue := fmt.Sprintf("arduino-cli/0.0.0-test.preview (amd64; linux; go1.12.4) Commit:deadbeef/Build:2019-06-12 11:11:11.111")
 	goldUserAgentString := "User-Agent: " + goldUserAgentValue