test(invocation): add command.Covers and subject consistency tests

Also improve the maintainability of the tests by a) providing a set of fixed Personas
and then generating a slew of valid delegation tokens, invalid delegation tokens
and proof-chains thereof.

did/didtest/crypto.go

@@ -0,0 +1,149 @@
+// Package didtest provides Personas that can be used for testing.  Each
+// Persona has a name, crypto.PrivKey and associated crypto.PubKey and
+// did.DID.
+package didtest
+
+import (
+	"sync"
+	"testing"
+
+	"github.com/libp2p/go-libp2p/core/crypto"
+	"github.com/stretchr/testify/require"
+	"github.com/ucan-wg/go-ucan/did"
+)
+
+const (
+	alicePrivKeyCfg = "CAESQHdNJLBBiuc1AdwPHBkubB2KS1p0cv2JEF7m8tfwtrcm5ajaYPm+XmVCmtcHOF2lGDlmaiDA7emfwD3IrcyES0M="
+	bobPrivKeyCfg   = "CAESQHBz+AIop1g+9iBDj+ufUc/zm9/ry7c6kDFO8Wl/D0+H63V9hC6s9l4npf3pYEFCjBtlR0AMNWMoFQKSlYNKo20="
+	carolPrivKeyCfg = "CAESQPrCgkcHnYFXDT9AlAydhPECBEivEuuVx9dJxLjVvDTmJIVNivfzg6H4mAiPfYS+5ryVVUZTHZBzvMuvvvG/Ks0="
+	danPrivKeyCfg   = "CAESQCgNhzofKhC+7hW6x+fNd7iMPtQHeEmKRhhlduf/I7/TeOEFYAEflbJ0sAhMeDJ/HQXaAvsWgHEbJ3ZLhP8q2B0="
+	erinPrivKeyCfg  = "CAESQKhCJo5UBpQcthko8DKMFsbdZ+qqQ5oc01CtLCqrE90dF2GfRlrMmot3WPHiHGCmEYi5ZMEHuiSI095e/6O4Bpw="
+	frankPrivKeyCfg = "CAESQDlXPKsy3jHh7OWTWQqyZF95Ueac5DKo7xD0NOBE5F2BNr1ZVxRmJ2dBELbOt8KP9sOACcO9qlCB7uMA1UQc7sk="
+)
+
+// Persona is a generic participant used for cryptographic testing.
+type Persona int
+
+// The provided  Personas were selected from the first few generic
+// participants listed in this [table].
+//
+// [table]: https://en.wikipedia.org/wiki/Alice_and_Bob#Cryptographic_systems
+const (
+	PersonaAlice Persona = iota
+	PersonaBob
+	PersonaCarol
+	PersonaDan
+	PersonaErin
+	PersonaFrank
+)
+
+var (
+	once     sync.Once
+	privKeys = make(map[Persona]crypto.PrivKey, 6)
+	err      error
+)
+
+// DID returns a did.DID based on the Persona's Ed25519 public key.
+func (p Persona) DID(t *testing.T) did.DID {
+	t.Helper()
+
+	did, err := did.FromPrivKey(p.PrivKey(t))
+	require.NoError(t, err)
+
+	return did
+}
+
+// Name returns the username of the Persona.
+func (p Persona) Name(t *testing.T) string {
+	t.Helper()
+
+	name, ok := map[Persona]string{
+		PersonaAlice: "Alice",
+		PersonaBob:   "Bob",
+		PersonaCarol: "Carol",
+		PersonaDan:   "Dan",
+		PersonaErin:  "Erin",
+		PersonaFrank: "Frank",
+	}[p]
+	if !ok {
+		t.Fatal("Unknown persona:", p)
+	}
+
+	return name
+}
+
+// PrivKey returns the Ed25519 private key for the Persona.
+func (p Persona) PrivKey(t *testing.T) crypto.PrivKey {
+	t.Helper()
+
+	once.Do(func() {
+		for persona, privKeyCfg := range privKeyCfgs(t) {
+			privKeyMar, err := crypto.ConfigDecodeKey(privKeyCfg)
+			if err != nil {
+				return
+			}
+
+			privKey, err := crypto.UnmarshalPrivateKey(privKeyMar)
+			if err != nil {
+				return
+			}
+
+			privKeys[persona] = privKey
+		}
+	})
+	require.NoError(t, err)
+
+	return privKeys[p]
+}
+
+// PrivKeyConfig returns the marshaled and encoded Ed25519 private key
+// for the Persona.
+func (p Persona) PrivKeyConfig(t *testing.T) string {
+	t.Helper()
+
+	return privKeyCfgs(t)[p]
+}
+
+// PubKey returns the Ed25519 public key for the Persona.
+func (p Persona) PubKey(t *testing.T) crypto.PubKey {
+	t.Helper()
+
+	return p.PrivKey(t).GetPublic()
+}
+
+// PubKeyConfig returns the marshaled and encoded Ed25519 public key
+// for the Persona.
+func (p Persona) PubKeyConfig(t *testing.T) string {
+	pubKeyMar, err := crypto.MarshalPublicKey(p.PrivKey(t).GetPublic())
+	require.NoError(t, err)
+
+	return crypto.ConfigEncodeKey(pubKeyMar)
+}
+
+func privKeyCfgs(t *testing.T) map[Persona]string {
+	t.Helper()
+
+	return map[Persona]string{
+		PersonaAlice: alicePrivKeyCfg,
+		PersonaBob:   bobPrivKeyCfg,
+		PersonaCarol: carolPrivKeyCfg,
+		PersonaDan:   danPrivKeyCfg,
+		PersonaErin:  erinPrivKeyCfg,
+		PersonaFrank: frankPrivKeyCfg,
+	}
+}
+
+// Personas returns an (alphabetically) ordered list of the defined
+// Persona values.
+func Personas(t *testing.T) []Persona {
+	t.Helper()
+
+	return []Persona{
+		PersonaAlice,
+		PersonaBob,
+		PersonaCarol,
+		PersonaDan,
+		PersonaErin,
+		PersonaFrank,
+	}
+}