Add test for previousProof fail.

suites/verify.js

@@ -274,7 +274,18 @@ export function runDataIntegrityProofVerifyTests({
           reason: 'Should not verify VC with invalid "proof.previousProof".'
         });
       });
+      it('Each value identifies another data integrity proof, all of which ' +
+      'MUST also verify for the current proof to be considered verified',
+      async function() {
+        this.test.link = 'https://w3c.github.io/vc-data-integrity/#:~:text=Each%20value%20identifies%20another%20data%20integrity%20proof%2C%20all%20of%20which%20MUST%20also%20verify%20for%20the%20current%20proof%20to%20be%20considered%20verified';
+        await verificationFail({
+          credential: credentials.clone('previousProofFail'),
+          verifier,
+          reason: 'Should not verify VC with a "previousProof" that does ' +
+          'not verify.'
+        });
 
+      });
     }
   });
 }

vc-generator/generators.js

@@ -41,6 +41,7 @@ export const generators = {
     invalidVm,
     undefinedTerm,
     previousProofString: defaultGen,
+    previousProofFail: defaultGen,
     previousProofArray: defaultGen,
     missingPreviousProofString: defaultGen,
     missingPreviousProofArray: defaultGen,
@@ -87,6 +88,28 @@ export const setups = {
       suites: [firstSuite, secondSuite]
     };
   },
+  previousProofFail({
+    cryptosuite,
+    signer,
+    mandatoryPointers,
+    selectivePointers,
+    proofId = 'urn:uuid:test:first:proof'
+
+  }) {
+    const {suite: firstSuite} = getSuites({
+      cryptosuite, signer,
+      mandatoryPointers, selectivePointers
+    });
+    firstSuite.proof = {id: proofId};
+    const {suite: secondSuite} = getSuites({
+      cryptosuite, signer,
+      mandatoryPointers, selectivePointers
+    });
+    secondSuite.proof = {previousProof: proofId};
+    return {
+      suites: [firstSuite, secondSuite]
+    };
+  },
   previousProofArray({
     cryptosuite,
     signer,
@@ -181,6 +204,11 @@ export const cleanups = {
       return !('@base' in c);
     });
     return issuedCredential;
+  },
+  previousProofFail({issuedCredential}) {
+    // make the first proof fail verification
+    issuedCredential.proof[0].proofValue = 'invalidProofValue';
+    return issuedCredential;
   }
 };
 /**