Refactor to separate FakeDownloader, DownloadWithCompression, repo download.

utils/fake.go

@@ -0,0 +1,85 @@
+package utils
+
+import (
+	"fmt"
+	"os"
+)
+
+type expectedRequest struct {
+	Url      string
+	Err      error
+	Response string
+}
+
+// FakeDownloader is like Downloader, but it used in tests
+// to stub out results
+type FakeDownloader struct {
+	expected []expectedRequest
+}
+
+// Check interface
+var (
+	_ Downloader = &FakeDownloader{}
+)
+
+// NewFakeDownloader creates new expected downloader
+func NewFakeDownloader() *FakeDownloader {
+	result := &FakeDownloader{}
+	result.expected = make([]expectedRequest, 0)
+	return result
+}
+
+// ExpectResponse installs expectation on upcoming download with response
+func (f *FakeDownloader) ExpectResponse(url string, response string) *FakeDownloader {
+	f.expected = append(f.expected, expectedRequest{Url: url, Response: response})
+	return f
+}
+
+// ExpectError installs expectation on upcoming download with error
+func (f *FakeDownloader) ExpectError(url string, err error) *FakeDownloader {
+	f.expected = append(f.expected, expectedRequest{Url: url, Err: err})
+	return f
+}
+
+// Empty verifies that are planned downloads have happened
+func (f *FakeDownloader) Empty() bool {
+	return len(f.expected) == 0
+}
+
+// Download performs fake download by matching against first expectation in the queue
+func (f *FakeDownloader) Download(url string, filename string) <-chan error {
+	result := make(chan error, 1)
+
+	if len(f.expected) == 0 || f.expected[0].Url != url {
+		result <- fmt.Errorf("unexpected request for %s", url)
+		return result
+	}
+
+	expected := f.expected[0]
+	f.expected = f.expected[1:]
+
+	if expected.Err != nil {
+		result <- expected.Err
+		return result
+	}
+
+	outfile, err := os.Create(filename)
+	if err != nil {
+		result <- err
+		return result
+	}
+	defer outfile.Close()
+
+	_, err = outfile.Write([]byte(expected.Response))
+	if err != nil {
+		result <- err
+		return result
+	}
+
+	result <- nil
+	return result
+}
+
+// Shutdown does nothing
+func (f *FakeDownloader) Shutdown() {
+}