Read the stored manifest through the record's own reader in the silent-file test

internal/inventory/stored_silent_file_test.go

@@ -39,11 +39,15 @@ func TestAStoredBuildWithASilentMergeableFileIsStillReadAndComposed(t *testing.T
 		t.Fatal(err)
 	}
 
-	kept, found, err := inv.BuildByID(ctx, b.ID)
-	if err != nil || !found {
-		t.Fatalf("the stored build is not read again: found %v, %v", found, err)
+	c, err := inv.theChain(ctx)
+	if err != nil {
+		t.Fatal(err)
 	}
-	m, err := catalogue.ParseManifest(kept.Manifest)
+	raw, err := inv.chainManifestOf(ctx, c, b.ID) // the manifest as the record keeps it, read from its digest when need be
+	if err != nil || len(raw) == 0 {
+		t.Fatalf("the stored build is not read again: %d bytes, %v", len(raw), err)
+	}
+	m, err := catalogue.ParseManifest(raw)
 	if err != nil {
 		t.Fatalf("the stored manifest is not read again: %v", err)
 	}