diff --git a/src/getHumanAge.test.js b/src/getHumanAge.test.js
index 6ce3e586..5499b659 100644
--- a/src/getHumanAge.test.js
+++ b/src/getHumanAge.test.js
@@ -7,4 +7,44 @@ describe('getHumanAge', () => {
     expect(getHumanAge)
       .toBeInstanceOf(Function);
   });
+
+  test('returns [0, 0] when both catAge and dogAge are 0', () => {
+    expect(getHumanAge(0, 0)).toEqual([0, 0]);
+  });
+
+  test('returns [0, 0] when both catAge and dogAge are less than 15', () => {
+    expect(getHumanAge(14, 14)).toEqual([0, 0]);
+  });
+
+  test('returns [1, 1] when both catAge and dogAge are exactly 15', () => {
+    expect(getHumanAge(15, 15)).toEqual([1, 1]);
+  });
+
+  test(
+    'returns [1, 1] when both catAge and dogAge are between 15 and 24',
+    () => expect(getHumanAge(23, 23)).toEqual([1, 1]),
+  );
+
+  test('returns [2, 2] when both catAge and dogAge are exactly 24', () => {
+    expect(getHumanAge(24, 24)).toEqual([2, 2]);
+  });
+
+  test('returns [2, 2] when both catAge and dogAge are 27', () => {
+    expect(getHumanAge(27, 27)).toEqual([2, 2]);
+  });
+
+  test(
+    'returns correct values when catAge and dogAge are different',
+    () => expect(getHumanAge(28, 27)).toEqual([3, 2]),
+  );
+
+  test(
+    'returns correct human years and handles large values',
+    () => expect(getHumanAge(100, 100)).toEqual([21, 17]),
+  );
+
+  test(
+    'correctly calculates different increments for cat and dog beyond 24 years',
+    () => expect(getHumanAge(28, 15)).toEqual([3, 1]),
+  );
 });