diff --git a/Tests/UnitTests.cs b/Tests/UnitTests.cs
index 5d5f6f41..793ab7d7 100644
--- a/Tests/UnitTests.cs
+++ b/Tests/UnitTests.cs
@@ -31,5 +31,102 @@ public void Add_Null()
         }
 
         // Implement 3 tests per operation, following a similar pattern as above
+        
+        [Test]
+        public void Subtract_Valid()
+        {
+            Assert.AreEqual(-1, Program.Subtract("1", "2"));
+            Assert.AreEqual(1, Program.Subtract("3", "2"));
+            Assert.AreEqual(-2, Program.Subtract("5", "7"));
+        }
+
+        [Test]
+        public void Subtract_Invalid()
+        {
+            Assert.Throws<FormatException>(() => Program.Subtract("1", "a"));
+            Assert.Throws<FormatException>(() => Program.Subtract("a", "1"));
+            Assert.Throws<FormatException>(() => Program.Subtract("a", "a"));
+        }
+
+        [Test]
+        public void Subtract_Null()
+        {
+            Assert.Throws<ArgumentNullException>(() => Program.Subtract("1", null));
+            Assert.Throws<ArgumentNullException>(() => Program.Subtract(null, "1"));
+            Assert.Throws<ArgumentNullException>(() => Program.Subtract(null, null));
+        }
+        
+        [Test]
+        public void Multiply_Valid()
+        {
+            Assert.AreEqual(2, Program.Multiply("1", "2"));
+            Assert.AreEqual(6, Program.Multiply("3", "2"));
+            Assert.AreEqual(35, Program.Multiply("5", "7"));
+        }
+
+        [Test]
+        public void Multiply_Invalid()
+        {
+            Assert.Throws<FormatException>(() => Program.Multiply("1", "a"));
+            Assert.Throws<FormatException>(() => Program.Multiply("a", "1"));
+            Assert.Throws<FormatException>(() => Program.Multiply("a", "a"));
+        }
+
+        [Test]
+        public void Multiply_Null()
+        {
+            Assert.Throws<ArgumentNullException>(() => Program.Multiply("1", null));
+            Assert.Throws<ArgumentNullException>(() => Program.Multiply(null, "1"));
+            Assert.Throws<ArgumentNullException>(() => Program.Multiply(null, null));
+        }
+        
+        [Test]
+        public void Divide_Valid()
+        {
+            Assert.AreEqual(2, Program.Divide("2", "1"));
+            Assert.AreEqual(1.5, Program.Divide("3", "2"), 0.001);
+            Assert.AreEqual(2.5, Program.Divide("17.5", "7"), 0.001);
+        }
+
+        [Test]
+        public void Divide_Invalid()
+        {
+            Assert.Throws<FormatException>(() => Program.Divide("1", "a"));
+            Assert.Throws<FormatException>(() => Program.Divide("a", "1"));
+            Assert.Throws<FormatException>(() => Program.Divide("a", "a"));
+        }
+
+        [Test]
+        public void Divide_Null()
+        {
+            Assert.Throws<ArgumentNullException>(() => Program.Divide("1", null));
+            Assert.Throws<ArgumentNullException>(() => Program.Divide(null, "1"));
+            Assert.Throws<ArgumentNullException>(() => Program.Divide(null, null));
+        }
+        
+        
+        [Test]
+        public void Power_Valid()
+        {
+            Assert.AreEqual(2, Program.Power("2", "1"));
+            Assert.AreEqual(9, Program.Power("3", "2"));
+            Assert.AreEqual(64, Program.Power("4", "3"));
+        }
+
+        [Test]
+        public void Power_Invalid()
+        {
+            Assert.Throws<FormatException>(() => Program.Power("1", "a"));
+            Assert.Throws<FormatException>(() => Program.Power("a", "1"));
+            Assert.Throws<FormatException>(() => Program.Power("a", "a"));
+        }
+
+        [Test]
+        public void Power_Null()
+        {
+            Assert.Throws<ArgumentNullException>(() => Program.Power("1", null));
+            Assert.Throws<ArgumentNullException>(() => Program.Power(null, "1"));
+            Assert.Throws<ArgumentNullException>(() => Program.Power(null, null));
+        }
     }
 }