diff --git a/src/test/java/fr/xephi/authme/util/PlayerUtilsTest.java b/src/test/java/fr/xephi/authme/util/PlayerUtilsTest.java
index be5425c2..d16a8547 100644
--- a/src/test/java/fr/xephi/authme/util/PlayerUtilsTest.java
+++ b/src/test/java/fr/xephi/authme/util/PlayerUtilsTest.java
@@ -64,4 +64,10 @@ public class PlayerUtilsTest {
         // then
         assertThat(result, equalTo(name));
     }
+
+    @Test
+    public void shouldHaveHiddenConstructor() {
+        // given / when / then
+        TestHelper.validateHasOnlyPrivateEmptyConstructor(PlayerUtils.class);
+    }
 }
diff --git a/src/test/java/fr/xephi/authme/util/RandomStringUtilsTest.java b/src/test/java/fr/xephi/authme/util/RandomStringUtilsTest.java
index c0f9cd0b..b5200b01 100644
--- a/src/test/java/fr/xephi/authme/util/RandomStringUtilsTest.java
+++ b/src/test/java/fr/xephi/authme/util/RandomStringUtilsTest.java
@@ -1,5 +1,6 @@
 package fr.xephi.authme.util;
 
+import fr.xephi.authme.TestHelper;
 import org.junit.Test;
 
 import java.util.regex.Pattern;
@@ -68,4 +69,10 @@ public class RandomStringUtilsTest {
         // then - throw exception
     }
 
+    @Test
+    public void shouldHaveHiddenConstructor() {
+        // given / when / then
+        TestHelper.validateHasOnlyPrivateEmptyConstructor(RandomStringUtils.class);
+    }
+
 }
diff --git a/src/test/java/fr/xephi/authme/util/lazytags/TagBuilderTest.java b/src/test/java/fr/xephi/authme/util/lazytags/TagBuilderTest.java
new file mode 100644
index 00000000..60b5b68e
--- /dev/null
+++ b/src/test/java/fr/xephi/authme/util/lazytags/TagBuilderTest.java
@@ -0,0 +1,50 @@
+package fr.xephi.authme.util.lazytags;
+
+import fr.xephi.authme.TestHelper;
+import org.junit.Test;
+
+import java.util.function.Function;
+import java.util.function.Supplier;
+
+import static org.hamcrest.Matchers.equalTo;
+import static org.hamcrest.Matchers.instanceOf;
+import static org.junit.Assert.assertThat;
+
+/**
+ * Test for {@link TagBuilder}.
+ */
+public class TagBuilderTest {
+
+    @Test
+    public void shouldCreateNoArgsTag() {
+        // given
+        Supplier<String> supplier = () -> "hello";
+
+        // when
+        Tag<String> tag = TagBuilder.createTag("hey", supplier);
+
+        // then
+        assertThat(tag, instanceOf(SimpleTag.class));
+        assertThat(tag.getValue(null), equalTo("hello"));
+    }
+
+    @Test
+    public void shouldCreateDependentTag() {
+        // given
+        Function<Double, String> function = d -> Double.toString(d + d/10);
+
+        // when
+        Tag<Double> tag = TagBuilder.createTag("%test", function);
+
+        // then
+        assertThat(tag, instanceOf(DependentTag.class));
+        assertThat(tag.getValue(24d), equalTo("26.4"));
+    }
+
+    @Test
+    public void shouldHaveHiddenConstructor() {
+        // given / when / then
+        TestHelper.validateHasOnlyPrivateEmptyConstructor(TagBuilder.class);
+    }
+
+}
diff --git a/src/test/java/fr/xephi/authme/util/lazytags/TagReplacerTest.java b/src/test/java/fr/xephi/authme/util/lazytags/TagReplacerTest.java
new file mode 100644
index 00000000..8c9a8187
--- /dev/null
+++ b/src/test/java/fr/xephi/authme/util/lazytags/TagReplacerTest.java
@@ -0,0 +1,90 @@
+package fr.xephi.authme.util.lazytags;
+
+import org.junit.Test;
+
+import java.util.Arrays;
+import java.util.List;
+
+import static fr.xephi.authme.util.lazytags.TagBuilder.createTag;
+import static org.hamcrest.Matchers.contains;
+import static org.hamcrest.Matchers.equalTo;
+import static org.junit.Assert.assertThat;
+
+/**
+ * Test for {@link TagReplacer}.
+ */
+public class TagReplacerTest {
+
+    @Test
+    public void shouldReplaceTags() {
+        // given
+        TestTagService tagService = new TestTagService();
+        List<Tag<Integer>> tags = tagService.getAvailableTags();
+        List<String> messages = Arrays.asList("pi = %PI", "for i = %self, i^2 = %square", "%self %self %PI");
+
+        // when
+        TagReplacer<Integer> tagReplacer = TagReplacer.newReplacer(tags, messages);
+        List<String> result = tagReplacer.getAdaptedMessages(3);
+
+        // then
+        assertThat(tagService.piCount, equalTo(1));
+        assertThat(tagService.selfCount, equalTo(1));
+        assertThat(tagService.doubleCount, equalTo(0));
+        assertThat(tagService.squareCount, equalTo(1));
+        assertThat(result, contains("pi = 3.14159", "for i = 3, i^2 = 9", "3 3 3.14159"));
+    }
+
+    @Test
+    public void shouldNotCallUnusedTags() {
+        // given
+        TestTagService tagService = new TestTagService();
+        List<Tag<Integer>> tags = tagService.getAvailableTags();
+        List<String> messages = Arrays.asList("pi = %PI", "double i = %double");
+
+        // when
+        TagReplacer<Integer> tagReplacer = TagReplacer.newReplacer(tags, messages);
+        List<String> result1 = tagReplacer.getAdaptedMessages(-4);
+        List<String> result2 = tagReplacer.getAdaptedMessages(0);
+
+        // then
+        assertThat(tagService.piCount, equalTo(2));
+        assertThat(tagService.selfCount, equalTo(0));
+        assertThat(tagService.doubleCount, equalTo(2));
+        assertThat(tagService.squareCount, equalTo(0));
+        assertThat(result1, contains("pi = 3.14159", "double i = -8"));
+        assertThat(result2, contains("pi = 3.14159", "double i = 0"));
+    }
+
+    static final class TestTagService {
+        int piCount, selfCount, doubleCount, squareCount;
+
+        String pi() {
+            ++piCount;
+            return "3.14159";
+        }
+
+        String self(int i) {
+            ++selfCount;
+            return Integer.toString(i);
+        }
+
+        String calcDouble(int i) {
+            ++doubleCount;
+            return Integer.toString(2 * i);
+        }
+
+        String calcSquare(int i) {
+            ++squareCount;
+            return Integer.toString(i * i);
+        }
+
+        List<Tag<Integer>> getAvailableTags() {
+            return Arrays.asList(
+                createTag("%PI", this::pi),
+                createTag("%self", this::self),
+                createTag("%double", this::calcDouble),
+                createTag("%square", this::calcSquare));
+        }
+    }
+
+}
diff --git a/src/test/java/fr/xephi/authme/util/lazytags/WrappedTagReplacerTest.java b/src/test/java/fr/xephi/authme/util/lazytags/WrappedTagReplacerTest.java
new file mode 100644
index 00000000..19915054
--- /dev/null
+++ b/src/test/java/fr/xephi/authme/util/lazytags/WrappedTagReplacerTest.java
@@ -0,0 +1,76 @@
+package fr.xephi.authme.util.lazytags;
+
+import fr.xephi.authme.util.lazytags.TagReplacerTest.TestTagService;
+import org.hamcrest.Description;
+import org.hamcrest.Matcher;
+import org.hamcrest.TypeSafeMatcher;
+import org.junit.Test;
+
+import java.util.Arrays;
+import java.util.List;
+
+import static org.hamcrest.Matchers.contains;
+import static org.hamcrest.Matchers.equalTo;
+import static org.junit.Assert.assertThat;
+
+/**
+ * Test for {@link WrappedTagReplacer}.
+ */
+public class WrappedTagReplacerTest {
+
+    @Test
+    public void shouldApplyTags() {
+        // given
+        TestTagService tagService = new TestTagService();
+        List<Tag<Integer>> tags = tagService.getAvailableTags();
+        List<SampleClass> objects = Arrays.asList(
+            new SampleClass(3, "pi is %PI"),
+            new SampleClass(5, "no tags here"),
+            new SampleClass(7, "i+i = %double"));
+
+        // when
+        WrappedTagReplacer<SampleClass, Integer> replacer = new WrappedTagReplacer<>(
+            tags, objects, SampleClass::getDescription, (o, s) -> new SampleClass(o.number, s));
+        List<SampleClass> result1 = replacer.getAdaptedItems(8);
+        List<SampleClass> result2 = replacer.getAdaptedItems(1);
+
+        // then
+        assertThat(tagService.piCount, equalTo(2));
+        assertThat(tagService.selfCount, equalTo(0));
+        assertThat(tagService.doubleCount, equalTo(2));
+        assertThat(tagService.squareCount, equalTo(0));
+        assertThat(result1, contains(
+            sampleClass(3, "pi is 3.14159"), sampleClass(5, "no tags here"), sampleClass(7, "i+i = 16")));
+        assertThat(result2, contains(
+            sampleClass(3, "pi is 3.14159"), sampleClass(5, "no tags here"), sampleClass(7, "i+i = 2")));
+    }
+
+
+    private static Matcher<SampleClass> sampleClass(int number, String description) {
+        return new TypeSafeMatcher<SampleClass>() {
+            @Override
+            protected boolean matchesSafely(SampleClass item) {
+                return number == item.number && description.equals(item.description);
+            }
+
+            @Override
+            public void describeTo(Description description) {
+                description.appendText("SampleClass[number=" + number + ";description=" + description + "]");
+            }
+        };
+    }
+
+    private static final class SampleClass {
+        private final int number;
+        private final String description;
+
+        SampleClass(int number, String description) {
+            this.number = number;
+            this.description = description;
+        }
+
+        String getDescription() {
+            return description;
+        }
+    }
+}