diff --git a/ClosedXML_Tests/Excel/CalcEngine/MathTrigTests.cs b/ClosedXML_Tests/Excel/CalcEngine/MathTrigTests.cs
index 5d258b4..dff451e 100644
--- a/ClosedXML_Tests/Excel/CalcEngine/MathTrigTests.cs
+++ b/ClosedXML_Tests/Excel/CalcEngine/MathTrigTests.cs
@@ -12,6 +12,20 @@
     {
         private readonly double tolerance = 1e-10;
 
+        [Theory]
+        public void Abs_ReturnsItselfOnPositiveNumbers([Range(0, 10, 0.1)] double input)
+        {
+            var actual = (double)XLWorkbook.EvaluateExpr(string.Format(@"ABS({0})", input.ToString(CultureInfo.InvariantCulture)));
+            Assert.AreEqual(input, actual, tolerance * 10);
+        }
+
+        [Theory]
+        public void Abs_ReturnsTheCorrectValueOnNegativeInput([Range(-10, -0.1, 0.1)] double input)
+        {
+            var actual = (double)XLWorkbook.EvaluateExpr(string.Format(@"ABS({0})", input.ToString(CultureInfo.InvariantCulture)));
+            Assert.AreEqual(-input, actual, tolerance * 10);
+        }
+
         [TestCase(-10, 3.041924001)]
         [TestCase(-9, 3.030935432)]
         [TestCase(-8, 3.017237659)]