test(docker): cover multi-RepoDigest update comparison

Restore the remaining focused regressions for the all-local-RepoDigests update comparison carried on the earlier core-runtime candidate: multi-digest resolution in getImageRepoDigests, false-update suppression in CheckImageUpdate, and the DigestsDiffer multi-digest cases. Test-only additions; the runtime change and contract sections are in the preceding fix(docker) commit.

Change-source: pulse-maintainer

internal/dockeragent/agent_image_digest_test.go

@@ -77,6 +77,42 @@ func TestAgent_getImageRepoDigest_FallbackToFirst(t *testing.T) {
 	}
 }
 
+func TestAgent_getImageRepoDigests_MultipleDigestsForOneImage(t *testing.T) {
+	agent := &Agent{
+		docker: &fakeDockerClient{
+			imageInspectWithRawFn: func(ctx context.Context, imageID string) (image.InspectResponse, []byte, error) {
+				return image.InspectResponse{
+					RepoDigests: []string{
+						"docker.io/library/postgres@sha256:44c4",
+						"docker.io/library/postgres@sha256:cf78",
+						"docker.io/other/postgres@sha256:beef",
+					},
+					Architecture: "amd64",
+					Os:           "linux",
+				}, nil, nil
+			},
+		},
+		logger: zerolog.New(io.Discard),
+	}
+
+	digests, arch, os, variant := agent.getImageRepoDigests(context.Background(), "image-id", "postgres:16.15-alpine3.24")
+	want := []string{"sha256:44c4", "sha256:cf78", "sha256:beef"}
+	if len(digests) != len(want) {
+		t.Fatalf("digests = %v, want %v", digests, want)
+	}
+	for i := range want {
+		if digests[i] != want[i] {
+			t.Fatalf("digests = %v, want %v", digests, want)
+		}
+	}
+	if arch != "amd64" || os != "linux" || variant != "" {
+		t.Fatalf("platform = %q/%q/%q, want amd64/linux/", arch, os, variant)
+	}
+	if got, _, _, _ := agent.getImageRepoDigest(context.Background(), "image-id", "postgres:16.15-alpine3.24"); got != "sha256:44c4" {
+		t.Fatalf("primary digest = %q, want sha256:44c4", got)
+	}
+}
+
 func TestAgent_getImageRepoDigest_InvalidRepoDigest(t *testing.T) {
 	agent := &Agent{
 		docker: &fakeDockerClient{

internal/dockeragent/registry_manifest_test.go

@@ -123,3 +123,43 @@ func TestRegistryChecker_MultiArchDigestLayersStayConsistentAcrossCache(t *testi
 		t.Fatalf("expected one HEAD and one GET before the cache hit, got %d requests", requestCount)
 	}
 }
+
+// Issue #2110: a local image can carry several RepoDigests, for example the
+// tag's manifest digest and a platform manifest digest. The update check must
+// treat any of them as the current image rather than reporting a false update
+// just because the first entry differs from the registry digest.
+func TestRegistryChecker_MultipleLocalRepoDigestsSuppressFalseUpdate(t *testing.T) {
+	checker := NewRegistryChecker(zerolog.Nop())
+	checker.httpClient = &http.Client{
+		Transport: roundTripFunc(func(req *http.Request) (*http.Response, error) {
+			if req.Method == http.MethodHead {
+				return newStringResponse(http.StatusOK, map[string]string{
+					"Content-Type":          "application/vnd.docker.distribution.manifest.v2+json",
+					"Docker-Content-Digest": "sha256:cf78",
+				}, ""), nil
+			}
+			return newStringResponse(http.StatusOK, nil, "{}"), nil
+		}),
+	}
+
+	result := checker.CheckImageUpdate(
+		context.Background(),
+		"example.test/postgres:16.15-alpine3.24",
+		"sha256:44c4,sha256:cf78",
+		"amd64",
+		"linux",
+		"",
+	)
+	if result == nil {
+		t.Fatal("expected an update result")
+	}
+	if result.UpdateAvailable {
+		t.Fatalf("a local RepoDigest matching the registry digest must suppress the update: %#v", result)
+	}
+	if result.CurrentDigest != "sha256:44c4" {
+		t.Fatalf("primary current digest = %q, want %q", result.CurrentDigest, "sha256:44c4")
+	}
+	if result.LatestDigest != "sha256:cf78" {
+		t.Fatalf("latest digest = %q, want %q", result.LatestDigest, "sha256:cf78")
+	}
+}

internal/dockeragent/registry_test.go

@@ -207,6 +207,24 @@ func TestRegistryChecker_DigestsDiffer(t *testing.T) {
 			latest:  "def456,abc123",
 			want:    true, // No match found
 		},
+		{
+			name:    "multiple current digests match second latest",
+			current: "sha256:44c4,sha256:cf78",
+			latest:  "sha256:cf78",
+			want:    false, // One local RepoDigest is current
+		},
+		{
+			name:    "multiple current digests no match",
+			current: "sha256:44c4,sha256:aaaa",
+			latest:  "sha256:cf78",
+			want:    true, // No local RepoDigest is current
+		},
+		{
+			name:    "empty entries in current set are ignored",
+			current: " ,sha256:cf78",
+			latest:  "sha256:cf78",
+			want:    false,
+		},
 	}
 
 	for _, tt := range tests {