test: make test layouts smaller

Author: mrjoelkamp

attestation/layout.go

@@ -103,7 +103,7 @@ func manifestFromOCILayout(path string, platform *v1.Platform) (*Manifest, error
 		// try the containerd annotation if the org.opencontainers.image.ref.name is not a full name
 		subjectName = idxDescriptor.Annotations[containerd.AnnotationImageName]
 		if _, err := reference.ParseNamed(subjectName); err != nil {
-			return nil, fmt.Errorf("failed to parse subject name from annotations")
+			return nil, fmt.Errorf("failed to find subject name in annotations")
 		}
 	}
 

attestation/layout_test.go

@@ -76,12 +76,12 @@ func TestSubjectNameAnnotations(t *testing.T) {
 	}{
 		{name: "oci annotation", ociLayoutPath: test.UnsignedTestImage("..")},
 		{name: "containerd annotation", ociLayoutPath: filepath.Join("..", "test", "testdata", "containerd-subject-layout")},
-		{name: "missing subject name", ociLayoutPath: filepath.Join("..", "test", "testdata", "missing-subject-layout"), errorStr: "failed to parse subject name from annotations"},
+		{name: "missing subject name", ociLayoutPath: filepath.Join("..", "test", "testdata", "missing-subject-layout"), errorStr: "failed to find subject name in annotations"},
 	}
 
 	for _, tc := range testCases {
 		t.Run(tc.name, func(t *testing.T) {
-			spec, err := oci.ParseImageSpec(oci.LocalPrefix + tc.ociLayoutPath)
+			spec, err := oci.ParseImageSpec(oci.LocalPrefix+tc.ociLayoutPath, oci.WithPlatform("linux/arm64"))
 			require.NoError(t, err)
 			_, err = policy.CreateImageDetailsResolver(spec)
 			if tc.errorStr != "" {