Add tests for isProperFraction function

Author: khaliun-dev

Sprint-3/1-implement-and-rewrite-tests/rewrite-tests-with-jest/2-is-proper-fraction.test.js

@@ -8,3 +8,37 @@ const isProperFraction = require("../implement/2-is-proper-fraction");
 test(`should return false when denominator is zero`, () => {
   expect(isProperFraction(1, 0)).toEqual(false);
 });
+
+// Proper fractions (positive numbers
+test(`should return true when numerator is smaller than denominator`, () => {
+  expect(isProperFraction(1, 2)).toEqual(true);
+  expect(isProperFraction(3, 4)).toEqual(true);
+});
+
+// Equal numbers → not proper
+test(`should return false when numerator equals denominator`, () => {
+  expect(isProperFraction(2, 2)).toEqual(false);
+});
+
+// Improper fractions
+test(`should return false when numerator is greater than denominator`, () => {
+  expect(isProperFraction(5, 4)).toEqual(false);
+  expect(isProperFraction(10, 3)).toEqual(false);
+});
+
+// Zero numerator
+test(`should return true when numerator is zero and denominator is non-zero`, () => {
+  expect(isProperFraction(0, 5)).toEqual(true);
+});
+
+// Negative numbers
+test(`should handle negative numbers correctly`, () => {
+  expect(isProperFraction(-1, 2)).toEqual(true);
+  expect(isProperFraction(1, -2)).toEqual(true);
+  expect(isProperFraction(-3, -2)).toEqual(false);
+});
+
+// Both zero
+test(`should return false when both numerator and denominator are zero`, () => {
+  expect(isProperFraction(0, 0)).toEqual(false);
+});