testing cache file exists

internal/cache/cache_test.go

@@ -0,0 +1,48 @@
+package cache
+
+import (
+	"bytes"
+	"fmt"
+	"net/http"
+	"net/http/httptest"
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+func newTestServer(t *testing.T, handler http.HandlerFunc) *httptest.Server {
+	t.Helper()
+	svr := httptest.NewServer(handler)
+	t.Cleanup(func() { svr.Close() })
+	return svr
+}
+
+func newTestCache(t *testing.T, mirrorURL string) *Cache {
+	t.Helper()
+	return NewCache(t.TempDir(), mirrorURL)
+}
+
+func TestFetchFileExists(t *testing.T) {
+	const expected = "This is fake file contents"
+
+	svr := newTestServer(t, http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		fmt.Fprint(w, expected)
+	}))
+
+	c := newTestCache(t, svr.URL+"/")
+
+	err := c.Fetch("fakefile")
+	if err != nil {
+		t.Fatalf("Fetch failed %v", err)
+	}
+
+	fakefilepath := filepath.Join(c.cacheRoot, "fakefile")
+
+	data, err := os.ReadFile(fakefilepath)
+	if err != nil {
+		t.Fatalf("Error reading file back: %v", err)
+	}
+	if !bytes.Equal(data, []byte(expected)) {
+		t.Errorf("expected file to contain %s got %s", expected, data)
+	}
+}