Add Tests for Heron's Formula (#3035)

src/main/java/com/thealgorithms/maths/HeronsFormula.java

@@ -0,0 +1,19 @@
+package com.thealgorithms.maths;
+
+/**
+ * Find the area of a triangle using only side lengths
+ */
+
+public class HeronsFormula {
+	
+	public static double Herons(int s1, int s2, int s3)
+	{
+		double a = s1;
+		double b = s2;
+		double c = s3;
+		double s = (a + b + c)/2.0;
+		double area = 0;
+		area = Math.sqrt((s)*(s-a)*(s-b)*(s-c));
+		return area;
+	}
+}

src/test/java/com/thealgorithms/maths/HeronsFormulaTest.java

@@ -0,0 +1,27 @@
+package com.thealgorithms.maths;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+public class HeronsFormulaTest {
+		@Test
+		void test1()
+		{
+			Assertions.assertEquals(HeronsFormula.Herons(3,4,5), 6.0);
+		}
+		@Test
+		void test2() 
+		{
+			Assertions.assertEquals(HeronsFormula.Herons(24,30,18), 216.0);
+		}
+		@Test
+		void test3()
+		{
+			Assertions.assertEquals(HeronsFormula.Herons(1,1,1), 0.4330127018922193);
+		}
+		@Test
+		void test4()
+		{
+			Assertions.assertEquals(HeronsFormula.Herons(4,5,8), 8.181534085976786);
+		}
+}