fix: report divide-by-zero on mod block instead of Not a Number

js/blocks/NumberBlocks.js

@@ -56,6 +56,10 @@ function setupNumberBlocks(activity) {
      */
     const handleMathError = (logo, error, blk, onError = NANERRORMSG) => {
         logo.stopTurtle = true;
+        if (error && error.message === "DivByZeroError") {
+            activity.errorMsg(ZERODIVIDEERRORMSG, blk);
+            return;
+        }
         activity.errorMsg(onError, blk);
     };
 

js/blocks/__tests__/NumberBlocks.test.js

@@ -283,6 +283,19 @@ describe("setupNumberBlocks", () => {
             expect(result).toEqual(0);
             global.MathUtility.doMod = (a, b) => Number(a) % Number(b);
         });
+
+        it("should call errorMsg with ZERODIVIDEERRORMSG when MathUtility.doMod throws DivByZeroError", () => {
+            activity.blocks.blockList[110] = { connections: [null, "c1", "c2"] };
+            logo.parseArg = jest.fn(() => 5);
+            global.MathUtility.doMod = () => {
+                throw new Error("DivByZeroError");
+            };
+            const modBlock = createdBlocks["mod"];
+            const result = modBlock.arg(logo, 0, 110, null);
+            expect(activity.errorMsg).toHaveBeenCalledWith(global.ZERODIVIDEERRORMSG, 110);
+            expect(result).toEqual(0);
+            global.MathUtility.doMod = (a, b) => Number(a) % Number(b);
+        });
     });
 
     describe("PowerBlock - extra branches", () => {

js/utils/__tests__/mathutils.test.js

@@ -130,7 +130,7 @@ describe("MathUtility", () => {
         });
 
         test("throws error for invalid inputs", () => {
-            expect(() => MathUtility.doMod("a", 3)).toThrow("Invalid number input");
+            expect(() => MathUtility.doMod("a", 3)).toThrow("NanError");
         });
 
         // Edge case tests
@@ -159,7 +159,7 @@ describe("MathUtility", () => {
         });
 
         test("throws error when second arg is string", () => {
-            expect(() => MathUtility.doMod(10, "a")).toThrow("Invalid number input");
+            expect(() => MathUtility.doMod(10, "a")).toThrow("NanError");
         });
     });
 
@@ -556,7 +556,7 @@ describe("MathUtility", () => {
 
     describe("edge cases - Infinity, NaN, and boundary values", () => {
         test("doMod throws an error when divisor is zero", () => {
-            expect(() => MathUtility.doMod(5, 0)).toThrow();
+            expect(() => MathUtility.doMod(5, 0)).toThrow("DivByZeroError");
         });
 
         test("doSqrt handles Infinity", () => {

js/utils/mathutils.js

@@ -130,11 +130,11 @@ class MathUtility {
     static doMod(a, b) {
         if (typeof a === "number" && typeof b === "number") {
             if (Number(b) === 0) {
-                throw new Error("Division by zero");
+                throw new Error("DivByZeroError");
             }
             return Number(a) % Number(b);
         } else {
-            throw new Error("Invalid number input");
+            throw new Error("NanError");
         }
     }