Cover proper fraction sign and boundary cases

Author: fatimarouchi

implement-and-rewrite-tests/implement-tests-with-node-test/2-is-proper-fraction.test.js

@@ -3,10 +3,31 @@ import test from "node:test";
 
 import { isProperFraction } from "../implement/2-is-proper-fraction.js";
 
-// TODO: Write tests to cover all cases.
-// What combinations of numerators and denominators should you test?
-
-test("Basic proper fraction", () => {
-  // Example: 1/2 is a proper fraction
+test("returns true when the numerator's magnitude is less than the denominator's", () => {
   assert.equal(isProperFraction(1, 2), true);
+  assert.equal(isProperFraction(-1, 2), true);
+  assert.equal(isProperFraction(1, -2), true);
+  assert.equal(isProperFraction(-1, -2), true);
+});
+
+test("returns false when the numerator's magnitude equals or exceeds the denominator's", () => {
+  assert.equal(isProperFraction(2, 2), false);
+  assert.equal(isProperFraction(-2, 2), false);
+  assert.equal(isProperFraction(2, -2), false);
+  assert.equal(isProperFraction(-2, -2), false);
+  assert.equal(isProperFraction(3, 2), false);
+  assert.equal(isProperFraction(-3, 2), false);
+  assert.equal(isProperFraction(3, -2), false);
+  assert.equal(isProperFraction(-3, -2), false);
+});
+
+test("returns true when the numerator is zero and the denominator is nonzero", () => {
+  assert.equal(isProperFraction(0, 5), true);
+  assert.equal(isProperFraction(0, -5), true);
+});
+
+test("returns false when the denominator is zero", () => {
+  assert.equal(isProperFraction(1, 0), false);
+  assert.equal(isProperFraction(-1, 0), false);
+  assert.equal(isProperFraction(0, 0), false);
 });