diff --git a/notifier/summary_test.go b/notifier/summary_test.go
new file mode 100644
index 0000000000..38854902f7
--- /dev/null
+++ b/notifier/summary_test.go
@@ -0,0 +1,107 @@
+package notifier
+
+import (
+	"context"
+	"testing"
+
+	"github.com/google/uuid"
+	"github.com/quay/claircore"
+	"github.com/quay/claircore/libvuln/driver"
+	"github.com/quay/claircore/test/log"
+
+	"github.com/quay/clair/v4/indexer"
+	"github.com/quay/clair/v4/matcher"
+)
+
+func TestNotificationSummary(t *testing.T) {
+	ctx := context.Background()
+	ctx, done := log.TestLogger(ctx, t)
+	defer done()
+
+	// This is a bunch of supporting data structures.
+	updater := uuid.New().String()
+	e := Event{
+		updater: updater,
+		uo: driver.UpdateOperation{
+			Ref:     uuid.New(),
+			Updater: updater,
+		},
+	}
+	manifest := "sha256:8d502da610b3c153d5aedaaf5323c0d49f61401d4791b4b1ffe9e36c6cbe09a0"
+	vs := []claircore.Vulnerability{
+		{ID: "🖳", Name: "uncool vulnerability"},
+		{ID: "☃", Name: "cool vulnerability", NormalizedSeverity: claircore.Critical},
+	}
+	am := claircore.AffectedManifests{
+		Vulnerabilities: map[string]*claircore.Vulnerability{
+			"☃": &vs[0],
+			"🖳": &vs[1],
+		},
+		VulnerableManifests: map[string][]string{},
+	}
+	for _, v := range vs {
+		am.VulnerableManifests[manifest] = append(am.VulnerableManifests[manifest], v.ID)
+	}
+	p := Processor{
+		matcher: &matcher.Mock{
+			UpdateDiff_: func(_ context.Context, prev, _ uuid.UUID) (*driver.UpdateDiff, error) {
+				if got, want := prev, uuid.Nil; got != want {
+					t.Errorf("got: %v, want: %v", got, want)
+				}
+				return &driver.UpdateDiff{
+					Added:   vs,
+					Removed: []claircore.Vulnerability{},
+				}, nil
+			},
+		},
+		indexer: &indexer.Mock{
+			AffectedManifests_: func(_ context.Context, vs []claircore.Vulnerability) (claircore.AffectedManifests, error) {
+				if len(vs) > 0 {
+					// Needs at least one affected manifest
+					// for the code path to invoke store.PutNotifications()
+					return am, nil
+				}
+				return claircore.NewAffectedManifests(), nil
+			},
+		},
+	}
+
+	// Enable summarization, set the check function.
+	p.NoSummary = false
+	p.store = &MockStore{
+		PutNotifications_: func(_ context.Context, o PutOpts) error {
+			t.Logf("got notification ID: %v", o.NotificationID)
+			for _, n := range o.Notifications {
+				t.Logf("manifest(%v): %v %v", n.Manifest, n.Reason, n.Vulnerability.Name)
+			}
+			if got, want := len(o.Notifications), 1; got != want {
+				t.Errorf("got: %d, want: %d", got, want)
+			}
+			if got, want := vs[1].Name, o.Notifications[0].Vulnerability.Name; got != want {
+				t.Errorf("got: %s, want: %s", got, want)
+			}
+			return nil
+		},
+	}
+	if err := p.create(ctx, e, uuid.Nil); err != nil {
+		t.Error(err)
+	}
+
+	// Disable summarization, swap the check function, and run again.
+	p.NoSummary = true
+	p.store = &MockStore{
+		PutNotifications_: func(_ context.Context, o PutOpts) error {
+			t.Logf("got notification ID: %v", o.NotificationID)
+			for _, n := range o.Notifications {
+				t.Logf("manifest(%v): %v %v", n.Manifest, n.Reason, n.Vulnerability.Name)
+			}
+			if got, want := len(o.Notifications), len(vs); got != want {
+				t.Errorf("got: %d, want: %d", got, want)
+			}
+			return nil
+		},
+	}
+	if err := p.create(ctx, e, uuid.Nil); err != nil {
+		t.Error(err)
+	}
+}