diff --git a/metropolis/node/labels_test.go b/metropolis/node/labels_test.go
new file mode 100644
index 0000000..0e8b799
--- /dev/null
+++ b/metropolis/node/labels_test.go
@@ -0,0 +1,26 @@
+package node
+
+import (
+	"errors"
+	"testing"
+)
+
+func TestValidateLabelKeyValue(t *testing.T) {
+	for i, te := range []struct {
+		in   string
+		want error
+	}{
+		{"foo", nil},
+		{"foo-bar.baz_barfoo", nil},
+		{"-", ErrLabelInvalidFirstCharacter},
+		{"-invalid", ErrLabelInvalidFirstCharacter},
+		{"invalid-", ErrLabelInvalidLastCharacter},
+		{"", ErrLabelEmpty},
+		{"accordingtoallknownlawsofaviationthereisnowaythatabeeshouldbeabletofly", ErrLabelTooLong},
+		{"example.com/annotation", ErrLabelInvalidCharacter},
+	} {
+		if got := ValidateLabel(te.in); !errors.Is(got, te.want) {
+			t.Errorf("%d: wanted %v, got %v", i, te.want, got)
+		}
+	}
+}