Add test case for IntegerToRoman (#3676)

src/test/java/com/thealgorithms/conversions/IntegerToRomanTest.java

@@ -0,0 +1,14 @@
+package com.thealgorithms.conversions;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+import org.junit.jupiter.api.Test;
+
+public class IntegerToRomanTest {
+
+    @Test
+    public void testIntegerToRoman() {
+        assertEquals("MCMXCIV", IntegerToRoman.integerToRoman(1994));
+        assertEquals("LVIII", IntegerToRoman.integerToRoman(58));
+    }
+}