BAEL 767 - Introduction to Apache Commons Math (update) (#1670)

* BAEL 767 - Introduction to apache commons math

* BAEL 767 - Moving examples to test classes

* BAEL 767 - Renaming tests with BDD convention

apache-commons-math/src/test/java/com/baeldung/commons/math/ComplexTests.java

@@ -0,0 +1,20 @@
+package com.baeldung.commons.math;
+
+import org.apache.commons.math3.complex.Complex;
+import org.junit.Assert;
+import org.junit.Test;
+
+public class ComplexTests {
+
+    @Test
+    public void whenComplexPow_thenCorrect() {
+        Complex first  = new Complex(1.0, 3.0);
+        Complex second = new Complex(2.0, 5.0);
+
+        Complex power = first.pow(second);
+
+        Assert.assertEquals(-0.007563724861696302, power.getReal(), 1e-7);
+        Assert.assertEquals(0.01786136835085382, power.getImaginary(), 1e-7);
+    }
+
+}