test(vc): add tests for the isVerifiable proof guard

packages/vc/src/verification/is-verifiable.test.ts

@@ -0,0 +1,60 @@
+import { describe, expect, it } from "vitest"
+
+import type { W3CCredential } from "../types"
+import { isVerifiable } from "./is-verifiable"
+
+// A minimal valid W3C credential, without a proof
+const baseCredential: W3CCredential = {
+  "@context": ["https://www.w3.org/2018/credentials/v1"],
+  type: ["VerifiableCredential"],
+  issuer: { id: "did:web:issuer.example.com" },
+  issuanceDate: "2025-01-01T00:00:00.000Z",
+  credentialSubject: { id: "did:web:subject.example.com" },
+}
+
+describe("isVerifiable", () => {
+  it("returns true when the credential carries a typed proof", () => {
+    const credential = { ...baseCredential, proof: { type: "JwtProof2020" } }
+    expect(isVerifiable(credential)).toBe(true)
+  })
+
+  it("returns true when the proof carries additional fields", () => {
+    const credential = {
+      ...baseCredential,
+      proof: { type: "JwtProof2020", jwt: "header.payload.signature" },
+    }
+    expect(isVerifiable(credential)).toBe(true)
+  })
+
+  it("returns false when no proof is present", () => {
+    expect(isVerifiable(baseCredential)).toBe(false)
+  })
+
+  it("returns false when proof is null", () => {
+    const credential = { ...baseCredential, proof: null }
+    expect(isVerifiable(credential)).toBe(false)
+  })
+
+  it("returns false when proof is present but undefined", () => {
+    const credential = { ...baseCredential, proof: undefined }
+    expect(isVerifiable(credential)).toBe(false)
+  })
+
+  it("returns false when proof is not an object", () => {
+    const credential = { ...baseCredential, proof: "JwtProof2020" }
+    expect(isVerifiable(credential)).toBe(false)
+  })
+
+  it("returns false when proof is an empty object", () => {
+    const credential = { ...baseCredential, proof: {} }
+    expect(isVerifiable(credential)).toBe(false)
+  })
+
+  it("returns false when proof has no type", () => {
+    const credential = {
+      ...baseCredential,
+      proof: { jwt: "header.payload.signature" },
+    }
+    expect(isVerifiable(credential)).toBe(false)
+  })
+})