if err != nil {
			t.Fatal(err)
		}

		// Fetch OCI image.
		binaryFetcher, actualDiget, err := fetcher.PrepareFetch(ref)
		if err != nil {
			t.Fatal(err)
		}
		actual, err := binaryFetcher()
		if err != nil {
			t.Fatal(err)
		}
		if string(actual) != exp {
			t.Errorf("ImageFetcher.binaryFetcher got %s, but want '%s'", string(actual), exp)
		}
		if actualDiget != d.Hex {

		return nil, fmt.Errorf("module downloaded from %v has checksum %v, which does not match: %v", key.downloadURL, dChecksum, key.checksum)
	}

	if binaryFetcher != nil {
		b, err = binaryFetcher()
		if err != nil {
			wasmRemoteFetchCount.With(resultTag.Value(downloadFailure)).Increment()
			return nil, fmt.Errorf("could not fetch Wasm binary: %v", err)
		}
	}

// Wasm binary is not fetched immediately, but returned by `binaryFetcher` function, which is returned by PrepareFetch.
// By this way, we can have another chance to check cache with `actualDigest` without downloading the OCI image.
func (o *ImageFetcher) PrepareFetch(url string) (binaryFetcher func() ([]byte, error), actualDigest string, err error) {
	ref, err := name.ParseReference(url)
	if err != nil {