diff --git a/src/test/java/software/leonov/common/util/function/NaturalOrderingTest.java b/src/test/java/software/leonov/common/util/function/NaturalOrderingTest.java
new file mode 100644
index 0000000..5ac8582
--- /dev/null
+++ b/src/test/java/software/leonov/common/util/function/NaturalOrderingTest.java
@@ -0,0 +1,78 @@
+package software.leonov.common.util.function;
+
+import static com.google.common.collect.Lists.newArrayList;
+import static com.google.common.truth.Truth.assertThat;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static software.leonov.common.util.function.CheckedComparator.evalUnchecked;
+import static software.leonov.common.util.function.CheckedComparator.naturalOrder;
+
+import java.util.List;
+
+import org.junit.jupiter.api.AfterAll;
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+class NaturalOrderingTest {
+
+    @BeforeAll
+    static void setUpBeforeClass() throws Exception {
+    }
+
+    @AfterAll
+    static void tearDownAfterClass() throws Exception {
+    }
+
+    @BeforeEach
+    void setUp() throws Exception {
+    }
+
+    @AfterEach
+    void tearDown() throws Exception {
+    }
+
+    @Test
+    void test_naturalOrder_strings() throws Exception {
+        final List<String> actual = newArrayList("b", "a", "d", "c");
+
+        actual.sort(evalUnchecked(naturalOrder()));
+
+        assertThat(actual).isEqualTo(newArrayList("a", "b", "c", "d"));
+    }
+
+    @Test
+    void test_naturalOrder_strings_reversed() throws Exception {
+        final List<String> actual = newArrayList("b", "a", "d", "c");
+
+        actual.sort(evalUnchecked(CheckedComparator.<String>naturalOrder().reversed()));
+
+        assertThat(actual).isEqualTo(newArrayList("d", "c", "b", "a"));
+    }
+
+    @Test
+    void test_naturalOrder_ints() throws Exception {
+        final List<Integer> actual = newArrayList(3, 7, 25, -6, 8, 5);
+
+        actual.sort(evalUnchecked(naturalOrder()));
+
+        assertThat(actual).isEqualTo(newArrayList(-6, 3, 5, 7, 8, 25));
+    }
+    
+    @Test
+    void test_naturalOrder_ints_reversed() throws Exception {
+        final List<Integer> actual = newArrayList(3, 7, 25, -6, 8, 5);
+
+        actual.sort(evalUnchecked(CheckedComparator.<Integer>naturalOrder().reversed()));
+
+        assertThat(actual).isEqualTo(newArrayList(25, 8, 7, 5, 3, -6));
+    }
+
+    @Test
+    void test_naturalOrder_ints_npe() throws Exception {
+        final List<Integer> actual = newArrayList(3, 7, 25, null, -6, 8, 5);
+
+        assertThrows(NullPointerException.class, () -> actual.sort(evalUnchecked(naturalOrder())));
+    }
+
+}
diff --git a/src/test/java/software/leonov/common/util/function/NullsTest.java b/src/test/java/software/leonov/common/util/function/NullsTest.java
new file mode 100644
index 0000000..07cb5c9
--- /dev/null
+++ b/src/test/java/software/leonov/common/util/function/NullsTest.java
@@ -0,0 +1,90 @@
+package software.leonov.common.util.function;
+
+import static com.google.common.collect.Lists.newArrayList;
+import static com.google.common.truth.Truth.assertThat;
+import static software.leonov.common.util.function.CheckedComparator.evalUnchecked;
+import static software.leonov.common.util.function.CheckedComparator.naturalOrder;
+import static software.leonov.common.util.function.CheckedComparator.nullsFirst;
+import static software.leonov.common.util.function.CheckedComparator.nullsLast;
+
+import java.util.List;
+
+import org.junit.jupiter.api.AfterAll;
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+class NullsTest {
+
+    @BeforeAll
+    static void setUpBeforeClass() throws Exception {
+    }
+
+    @AfterAll
+    static void tearDownAfterClass() throws Exception {
+    }
+
+    @BeforeEach
+    void setUp() throws Exception {
+    }
+
+    @AfterEach
+    void tearDown() throws Exception {
+    }
+
+    @Test
+    void test_nullsFirst_naturalOrder() throws Exception {
+        final List<String> actual = newArrayList("b", "a", null, "d", "c", null);
+
+        actual.sort(evalUnchecked(nullsFirst(naturalOrder())));
+
+        assertThat(actual).isEqualTo(newArrayList(null, null, "a", "b", "c", "d"));
+    }
+
+    @Test
+    void test_nullsFirst_naturalOrder_reversed() throws Exception {
+        final List<String> actual = newArrayList("b", "a", null, "d", "c", null);
+
+        actual.sort(evalUnchecked(nullsFirst(CheckedComparator.<String>naturalOrder()).reversed()));
+
+        assertThat(actual).isEqualTo(newArrayList("d", "c", "b", "a", null, null));
+    }
+
+    @Test
+    void test_nullsLast_naturalOrder() throws Exception {
+        final List<String> actual = newArrayList("b", "a", null, "d", "c", null);
+
+        actual.sort(evalUnchecked(nullsLast(naturalOrder())));
+
+        assertThat(actual).isEqualTo(newArrayList("a", "b", "c", "d", null, null));
+    }
+
+    @Test
+    void test_nullsLast_naturalOrder_reversed() throws Exception {
+        final List<String> actual = newArrayList("b", "a", null, "d", "c", null);
+
+        actual.sort(evalUnchecked(nullsLast(CheckedComparator.<String>naturalOrder()).reversed()));
+
+        assertThat(actual).isEqualTo(newArrayList(null, null, "d", "c", "b", "a"));
+    }
+
+    @Test
+    void test_nullsFirst_null() throws Exception {
+        final List<String> actual = newArrayList("b", "a", null, "d", "c", null);
+
+        actual.sort(evalUnchecked(nullsFirst(null)));
+
+        assertThat(actual).isEqualTo(newArrayList(null, null, "b", "a", "d", "c"));
+    }
+
+    @Test
+    void test_nullsFirst_last() throws Exception {
+        final List<String> actual = newArrayList("b", "a", null, "d", "c", null);
+
+        actual.sort(evalUnchecked(nullsLast(null)));
+
+        assertThat(actual).isEqualTo(newArrayList("b", "a", "d", "c", null, null));
+    }
+
+}
diff --git a/src/test/java/software/leonov/common/util/function/Test.java b/src/test/java/software/leonov/common/util/function/Test.java
deleted file mode 100644
index f1811be..0000000
--- a/src/test/java/software/leonov/common/util/function/Test.java
+++ /dev/null
@@ -1,27 +0,0 @@
-package software.leonov.common.util.function;
-
-import static software.leonov.common.util.function.CheckedFunction.evalUnchecked;
-
-import java.io.IOException;
-import java.net.MalformedURLException;
-import java.net.URL;
-import java.util.stream.Stream;
-
-public class Test {
-
-    public static void main(String[] args) throws IOException {
-        
-        
-        Stream.of("https://www.google.com").map(t -> {
-            try {
-                return new URL(t);
-            } catch (MalformedURLException e) {
-                throw new RuntimeException(e);
-            }
-        });
-        
-        Stream.of("https://www.google.com").map(evalUnchecked(URL::new));
-        
-    }
-
-}