test: fuzz testing for circuits

circuits/circom/utils/calculateTotal.circom

@@ -14,7 +14,7 @@ template CalculateTotal(n) {
     signal sums[n];
     sums[0] <== nums[0];
 
-    for (var i=1; i < n; i++) {
+    for (var i = 1; i < n; i++) {
         sums[i] <== sums[i - 1] + nums[i];
     }
 

circuits/circom/utils/privToPubKey.circom

@@ -2,6 +2,7 @@ pragma circom 2.0.0;
 
 // circomlib imports
 include "./bitify.circom";
+include "./comparators.circom";
 include "./escalarmulfix.circom";
 
 /**
@@ -15,9 +16,16 @@ template PrivToPubKey() {
         16950150798460657717958625567821834550301663161624707787222815936182638968203
     ];
 
+    // Prime subgroup order 'l'.
+    var l = 2736030358979909402780800718157159386076813972158567259200215660948447373041;
+
     signal input privKey;
     signal output pubKey[2];
 
+    // Check if private key is in the prime subgroup order 'l'
+    var isLessThan = LessThan(251)([privKey, l]);
+    isLessThan === 1;
+
     // Convert the private key to bits.
     var computedPrivBits[253] = Num2Bits(253)(privKey);
 

circuits/package.json

@@ -20,19 +20,21 @@
     "circom:build": "NODE_OPTIONS=--max-old-space-size=4096 circomkit compile",
     "circom:setup": "NODE_OPTIONS=--max-old-space-size=4096 circomkit setup",
     "types": "tsc -p tsconfig.json --noEmit",
-    "test": "ts-mocha --exit ts/__tests__/*.test.ts",
-    "test:hasher": "ts-mocha --exit ts/__tests__/Hasher.test.ts",
-    "test:slAndBallotTransformer": "ts-mocha --exit ts/__tests__/StateLeafAndBallotTransformer.test.ts",
-    "test:messageToCommand": "ts-mocha --exit ts/__tests__/MessageToCommand.test.ts",
-    "test:messageValidator": "ts-mocha --exit ts/__tests__/MessageValidator.test.ts",
-    "test:verifySignature": "ts-mocha --exit ts/__tests__/VerifySignature.test.ts",
-    "test:splicer": "ts-mocha --exit ts/__tests__/Splicer.test.ts",
-    "test:privToPubKey": "ts-mocha --exit ts/__tests__/PrivToPubKey.test.ts",
-    "test:calculateTotal": "ts-mocha --exit ts/__tests__/CalculateTotal.test.ts",
-    "test:processMessages": "NODE_OPTIONS=--max-old-space-size=4096 ts-mocha --exit ts/__tests__/ProcessMessages.test.ts",
-    "test:tallyVotes": "NODE_OPTIONS=--max-old-space-size=4096 ts-mocha --exit ts/__tests__/TallyVotes.test.ts",
-    "test:ceremonyParams": "ts-mocha --exit ts/__tests__/CeremonyParams.test.ts",
-    "test:incrementalQuinaryTree": "ts-mocha --exit ts/__tests__/IncrementalQuinaryTree.test.ts"
+    "mocha-test": "NODE_OPTIONS=--max-old-space-size=4096 ts-mocha --exit -g '^(?!.*\\[fuzz\\]).*$'",
+    "test": "pnpm run mocha-test ts/__tests__/*.test.ts",
+    "test:fuzz": "NODE_OPTIONS=--max-old-space-size=4096 ts-mocha --exit -g '\\[fuzz\\]' ./ts/__tests__/*.test.ts",
+    "test:hasher": "pnpm run mocha-test ts/__tests__/Hasher.test.ts",
+    "test:slAndBallotTransformer": "pnpm run mocha-test ts/__tests__/StateLeafAndBallotTransformer.test.ts",
+    "test:messageToCommand": "pnpm run mocha-test ts/__tests__/MessageToCommand.test.ts",
+    "test:messageValidator": "pnpm run mocha-test ts/__tests__/MessageValidator.test.ts",
+    "test:verifySignature": "pnpm run mocha-test ts/__tests__/VerifySignature.test.ts",
+    "test:splicer": "pnpm run mocha-test ts/__tests__/Splicer.test.ts",
+    "test:privToPubKey": "pnpm run mocha-test ts/__tests__/PrivToPubKey.test.ts",
+    "test:calculateTotal": "pnpm run mocha-test ts/__tests__/CalculateTotal.test.ts",
+    "test:processMessages": "pnpm run mocha-test ts/__tests__/ProcessMessages.test.ts",
+    "test:tallyVotes": "pnpm run mocha-test ts/__tests__/TallyVotes.test.ts",
+    "test:ceremonyParams": "pnpm run mocha-test ts/__tests__/CeremonyParams.test.ts",
+    "test:incrementalQuinaryTree": "pnpm run mocha-test ts/__tests__/IncrementalQuinaryTree.test.ts"
   },
   "dependencies": {
     "@zk-kit/circuits": "^0.4.0",
@@ -48,8 +50,10 @@
     "@types/chai-as-promised": "^7.1.8",
     "@types/mocha": "^10.0.6",
     "@types/node": "^20.12.12",
+    "@zk-kit/baby-jubjub": "^1.0.1",
     "chai": "^4.3.10",
     "chai-as-promised": "^7.1.2",
+    "fast-check": "^3.18.0",
     "mocha": "^10.4.0",
     "ts-mocha": "^10.0.0",
     "ts-node": "^10.9.1",

circuits/ts/__tests__/CalculateTotal.test.ts

@@ -1,8 +1,12 @@
+import { r } from "@zk-kit/baby-jubjub";
 import { type WitnessTester } from "circomkit";
+import fc from "fast-check";
 
-import { circomkitInstance } from "./utils/utils";
+import { circomkitInstance, getSignal } from "./utils/utils";
+
+describe("CalculateTotal circuit", function test() {
+  this.timeout(900000);
 
-describe("CalculateTotal circuit", () => {
   let circuit: WitnessTester<["nums"], ["sum"]>;
 
   before(async () => {
@@ -15,6 +19,7 @@ describe("CalculateTotal circuit", () => {
 
   it("should correctly sum a list of values", async () => {
     const nums: number[] = [];
+
     for (let i = 0; i < 6; i += 1) {
       nums.push(Math.floor(Math.random() * 100));
     }
@@ -27,4 +32,44 @@ describe("CalculateTotal circuit", () => {
 
     await circuit.expectPass(circuitInputs, { sum });
   });
+
+  it("should sum max value and loop back", async () => {
+    const nums: bigint[] = [r, r, r, r, r, r];
+
+    await circuit.expectPass({ nums }, { sum: 0n });
+  });
+
+  it("should sum max negative value and loop back", async () => {
+    const nums: bigint[] = [-r, -r, -r, -r, -r, -r];
+
+    await circuit.expectPass({ nums }, { sum: 0n });
+  });
+
+  it("should sum max positive and negative values without looping", async () => {
+    const nums: bigint[] = [-r, r, -r, r, 1n, 2n];
+
+    await circuit.expectPass({ nums }, { sum: 3n });
+  });
+
+  it("should correctly sum a list of values [fuzz]", async () => {
+    await fc.assert(
+      fc.asyncProperty(fc.array(fc.bigInt({ min: 0n, max: r - 1n }), { minLength: 1 }), async (nums: bigint[]) => {
+        const sum = nums.reduce((a, b) => a + b, 0n);
+        fc.pre(sum <= r - 1n);
+
+        const testCircuit = await circomkitInstance.WitnessTester("calculateTotal", {
+          file: "./utils/calculateTotal",
+          template: "CalculateTotal",
+          params: [nums.length],
+        });
+
+        const witness = await testCircuit.calculateWitness({ nums });
+        await testCircuit.expectConstraintPass(witness);
+        const total = await getSignal(testCircuit, witness, "sum");
+
+        return total === sum;
+      }),
+      { numRuns: 10_000 },
+    );
+  });
 });