tests(library/math): completes spec for in-scope failure mode of greatestCommonDivisor (#545)

- see [commits](https://github.com/nod-ai/shark-ui/pull/545/commits) for details

Author: bjacobgordon

src/library/math/operator/constructive/greatestCommonDivisor.test.ts

@@ -4,6 +4,8 @@ import {
   expect,
 } from 'vitest';
 
+import Attempt from '@/library/Attempt';
+
 import {
   numberTaxonomy,
 } from '../../numberTaxonomy';
@@ -72,8 +74,10 @@ describe(greatestCommonDivisor, () => {
 
     describe('when generated', () => {
       describe('due to fractional operands', () => {
+        const eulers = numberTaxonomy.fractional.transcendental; // c-spell:words eulers
+
         const combosOfFractionalNumbers = symmetricPairCombos({
-          of    : numberTaxonomy.fractional.transcendental,
+          of    : eulers,
           filler: primeA,
         });
 
@@ -83,9 +87,32 @@ describe(greatestCommonDivisor, () => {
           expect(() => greatestCommonDivisor(...$0)).toThrow(Error);
         });
 
-        it.todo('should safely propagate the error');
+        it.each(combosOfFractionalNumbers)('should safely propagate the error', (...$0) => {
+          expect.assertions(1);
+
+          expect(() => greatestCommonDivisor(...$0)).toThrow(Attempt.NonActionableError);
+        });
+
+        const fractionalCombosWithMessage = [
+          {
+            numbers: [eulers, primeA] as const,
+            message: 'Left operand must be whole.',
+          },
+          {
+            numbers: [eulers, eulers] as const,
+            message: 'Left operand must be whole.',
+          },
+          {
+            numbers: [primeA, eulers] as const,
+            message: 'Right operand must be whole.',
+          },
+        ];
+
+        it.each(fractionalCombosWithMessage)('should communicate clearly with developers', ($0) => {
+          expect.assertions(1);
 
-        it.todo('should communicate clearly with developers');
+          expect(() => greatestCommonDivisor(...$0.numbers)).toThrow($0.message);
+        });
       });
     });
   });