diff --git a/build.gradle b/build.gradle
index 105cc481..23dbfb1d 100644
--- a/build.gradle
+++ b/build.gradle
@@ -61,6 +61,10 @@ allprojects {
         annotationProcessor 'org.projectlombok:lombok:1.18.20'
         testCompileOnly 'org.projectlombok:lombok:1.18.20'
         testAnnotationProcessor 'org.projectlombok:lombok:1.18.20'
+
+        // Test
+        testImplementation 'org.junit.jupiter:junit-jupiter-api:5.3.1'
+        testRuntimeOnly 'org.junit.jupiter:junit-jupiter-engine:5.3.1'
     }
 
     tasks.withType(JavaCompile) {
@@ -96,6 +100,18 @@ allprojects {
         withSourcesJar()
     }
 
+    test {
+        useJUnitPlatform()
+
+        // Always run tests, even when nothing changed.
+        dependsOn cleanTest
+
+        // Show test results.
+        testLogging {
+            events "passed", "skipped", "failed"
+        }
+    }
+
     compileJava.options.encoding = 'UTF-8'
     compileJava.dependsOn clean
 
diff --git a/eco-api/src/test/java/NumberUtilsTest.java b/eco-api/src/test/java/NumberUtilsTest.java
new file mode 100644
index 00000000..22fc23d4
--- /dev/null
+++ b/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(NumberUtils.format(3.0D), "3");
+        Assertions.assertEquals(NumberUtils.format(3.2D), "3.20");
+    }
+
+    @Test
+    public void testLog2() {
+        Assertions.assertEquals(NumberUtils.log2(2), 1);
+    }
+
+    @Test
+    public void testNumerals() {
+        Assertions.assertEquals(NumberUtils.fromNumeral("IV"), 4);
+        Assertions.assertEquals(NumberUtils.fromNumeral("IX"), 9);
+        Assertions.assertEquals(NumberUtils.toNumeral(14), "XIV");
+        Assertions.assertEquals(NumberUtils.toNumeral(21), "XXI");
+    }
+}