Move cover bytes to filesystem storage

backend/main_test.go

@@ -37,6 +37,13 @@ func TestLoadLatestPollDefaults(t *testing.T) {
 	}
 }
 
+func TestLoadConfigReadsCoverDirectory(t *testing.T) {
+	t.Setenv("COVER_DIR", "/covers")
+	if got := loadConfig().CoverDir; got != "/covers" {
+		t.Fatalf("CoverDir = %q, want /covers", got)
+	}
+}
+
 func TestLoadLatestPollEnabledParsing(t *testing.T) {
 	tests := []struct {
 		raw  string