diff --git a/.travis.yml b/.travis.yml
index 739464ec..9d791276 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -6,4 +6,5 @@ branches:
 install:
   - nuget restore TravisCI.sln
 script:
-  - msbuild /p:Configuration=Release TravisCI.sln
\ No newline at end of file
+  - msbuild /p:Configuration=Release TravisCI.sln
+  - mono ./packages/NUnit.ConsoleRunner.*/tools/nunit3-console.exe ./Tests/bin/Release/Tests.dll
\ No newline at end of file
diff --git a/Tests/UnitTests.cs b/Tests/UnitTests.cs
index 84cde036..dcfb2cc1 100644
--- a/Tests/UnitTests.cs
+++ b/Tests/UnitTests.cs
@@ -31,5 +31,100 @@ 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(3, Program.Divide("3", "1"));
+            Assert.AreEqual(2, Program.Divide("4", "2"));
+        }
+
+        [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(1, Program.Power("1", "2"));
+            Assert.AreEqual(9, Program.Power("3", "2"));
+            Assert.AreEqual(125, Program.Power("5", "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));
+        }
     }
 }