Gave up trying to have separate java and kotlin modules

eco-api/src/test/java/NumberUtilsTest.java

@@ -0,0 +1,24 @@
+import com.willfp.eco.util.NumberUtils;
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+public class NumberUtilsTest {
+    @Test
+    public void testFormatDouble() {
+        Assertions.assertEquals("3", NumberUtils.format(3.0D));
+        Assertions.assertEquals("3.20", NumberUtils.format(3.2D));
+    }
+
+    @Test
+    public void testLog2() {
+        Assertions.assertEquals(1, NumberUtils.log2(2));
+    }
+
+    @Test
+    public void testNumerals() {
+        Assertions.assertEquals(4, NumberUtils.fromNumeral("IV"));
+        Assertions.assertEquals(9, NumberUtils.fromNumeral("IX"));
+        Assertions.assertEquals("XIV", NumberUtils.toNumeral(14));
+        Assertions.assertEquals("XXI", NumberUtils.toNumeral(21));
+    }
+}