move artifact package over

Signed-off-by: Meredith Lancaster <malancas@github.com>

pkg/cmd/attestation/artifact/image_test.go

@@ -0,0 +1,41 @@
+package artifact
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/github/gh-attestation/pkg/artifact/oci"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestDigestContainerImageArtifact(t *testing.T) {
+	expectedDigest := "1234567890abcdef"
+	client := oci.NewMockClient()
+	url := "example.com/repo:tag"
+	digestedArtifact, err := digestContainerImageArtifact(url, client)
+	assert.NoError(t, err)
+	assert.Equal(t, fmt.Sprintf("oci://%s", url), digestedArtifact.URL)
+	assert.Equal(t, expectedDigest, digestedArtifact.digest)
+	assert.Equal(t, "sha256", digestedArtifact.digestAlg)
+}
+
+func TestFetchImageFailure(t *testing.T) {
+	client := oci.NewReferenceFailClient()
+	url := "example.com/repo:tag"
+	_, err := digestContainerImageArtifact(url, client)
+	assert.Error(t, err)
+}
+
+func TestRegistryAuthFailure(t *testing.T) {
+	client := oci.NewAuthFailClient()
+	url := "example.com/repo:tag"
+	_, err := digestContainerImageArtifact(url, client)
+	assert.ErrorIs(t, err, oci.ErrRegistryAuthz)
+}
+
+func TestDeniedFailure(t *testing.T) {
+	client := oci.NewDeniedClient()
+	url := "example.com/repo:tag"
+	_, err := digestContainerImageArtifact(url, client)
+	assert.ErrorIs(t, err, oci.ErrDenied)
+}