diff --git a/src/main/java/org/cqfn/astranaut/core/base/Position.java b/src/main/java/org/cqfn/astranaut/core/base/Position.java
index c235655..391b181 100644
--- a/src/main/java/org/cqfn/astranaut/core/base/Position.java
+++ b/src/main/java/org/cqfn/astranaut/core/base/Position.java
@@ -51,14 +51,6 @@ public interface Position extends Comparable<Position> {
      */
     int getColumn();
 
-    /**
-     * Compares this position with the specified position for order.
-     * @param other The position to be compared
-     * @return A negative integer, zero, or a positive integer as this position is less than,
-     *  equal to, or greater than the specified position.
-     * @throws IllegalArgumentException If positions are from different sources and cannot
-     *  be compared
-     */
     @Override
     default int compareTo(final Position other) {
         if (!this.getSource().equals(other.getSource())) {
diff --git a/src/test/java/org/cqfn/astranaut/core/base/DifferenceNodeTest.java b/src/test/java/org/cqfn/astranaut/core/base/DiffNodeTest.java
similarity index 89%
rename from src/test/java/org/cqfn/astranaut/core/base/DifferenceNodeTest.java
rename to src/test/java/org/cqfn/astranaut/core/base/DiffNodeTest.java
index 519657f..d7390ec 100644
--- a/src/test/java/org/cqfn/astranaut/core/base/DifferenceNodeTest.java
+++ b/src/test/java/org/cqfn/astranaut/core/base/DiffNodeTest.java
@@ -36,7 +36,7 @@
  *
  * @since 1.1.0
  */
-class DifferenceNodeTest {
+class DiffNodeTest {
     /**
      * The folder with test resources.
      */
@@ -82,12 +82,12 @@ class DifferenceNodeTest {
      */
     @Test
     void testInsertGetBefore() {
-        final Node root = this.loadTree(DifferenceNodeTest.TREE_WITH_INSERT);
+        final Node root = this.loadTree(DiffNodeTest.TREE_WITH_INSERT);
         Assertions.assertTrue(root instanceof DiffNode);
         final DiffNode diff = (DiffNode) root;
         final Node actual = diff.getBefore();
         Assertions.assertNotEquals(EmptyTree.INSTANCE, actual);
-        final Node expected = this.loadTree(DifferenceNodeTest.TREE_AFTER_DELETE);
+        final Node expected = this.loadTree(DiffNodeTest.TREE_AFTER_DELETE);
         Assertions.assertTrue(expected.deepCompare(actual));
     }
 
@@ -96,12 +96,12 @@ void testInsertGetBefore() {
      */
     @Test
     void testInsertGetAfter() {
-        final Node root = this.loadTree(DifferenceNodeTest.TREE_WITH_INSERT);
+        final Node root = this.loadTree(DiffNodeTest.TREE_WITH_INSERT);
         Assertions.assertTrue(root instanceof DiffNode);
         final DiffNode diff = (DiffNode) root;
         final Node actual = diff.getAfter();
         Assertions.assertNotEquals(EmptyTree.INSTANCE, actual);
-        final Node expected = this.loadTree(DifferenceNodeTest.TREE_BEFO_DELETE);
+        final Node expected = this.loadTree(DiffNodeTest.TREE_BEFO_DELETE);
         Assertions.assertTrue(expected.deepCompare(actual));
     }
 
@@ -110,18 +110,18 @@ void testInsertGetAfter() {
      */
     @Test
     void testReplace() {
-        final Node root = this.loadTree(DifferenceNodeTest.TREE_WITH_REPLACE);
+        final Node root = this.loadTree(DiffNodeTest.TREE_WITH_REPLACE);
         Assertions.assertTrue(root instanceof DiffNode);
         final DiffNode diff = (DiffNode) root;
         final Node before = diff.getBefore();
         Assertions.assertNotEquals(EmptyTree.INSTANCE, before);
         Assertions.assertTrue(
-            before.deepCompare(this.loadTree(DifferenceNodeTest.TREE_BEFORE_REPL))
+            before.deepCompare(this.loadTree(DiffNodeTest.TREE_BEFORE_REPL))
         );
         final Node after = diff.getAfter();
         Assertions.assertNotEquals(EmptyTree.INSTANCE, after);
         Assertions.assertTrue(
-            after.deepCompare(this.loadTree(DifferenceNodeTest.TREE_AFTER_REPL))
+            after.deepCompare(this.loadTree(DiffNodeTest.TREE_AFTER_REPL))
         );
     }
 
@@ -130,12 +130,12 @@ void testReplace() {
      */
     @Test
     void testDeleteGetBefore() {
-        final Node root = this.loadTree(DifferenceNodeTest.TREE_WITH_DELETE);
+        final Node root = this.loadTree(DiffNodeTest.TREE_WITH_DELETE);
         Assertions.assertTrue(root instanceof DiffNode);
         final DiffNode diff = (DiffNode) root;
         final Node actual = diff.getBefore();
         Assertions.assertNotEquals(EmptyTree.INSTANCE, actual);
-        final Node expected = this.loadTree(DifferenceNodeTest.TREE_BEFO_DELETE);
+        final Node expected = this.loadTree(DiffNodeTest.TREE_BEFO_DELETE);
         Assertions.assertTrue(expected.deepCompare(actual));
     }
 
@@ -144,12 +144,12 @@ void testDeleteGetBefore() {
      */
     @Test
     void testDeleteGetAfter() {
-        final Node root = this.loadTree(DifferenceNodeTest.TREE_WITH_DELETE);
+        final Node root = this.loadTree(DiffNodeTest.TREE_WITH_DELETE);
         Assertions.assertTrue(root instanceof DiffNode);
         final DiffNode diff = (DiffNode) root;
         final Node actual = diff.getAfter();
         Assertions.assertNotEquals(EmptyTree.INSTANCE, actual);
-        final Node expected = this.loadTree(DifferenceNodeTest.TREE_AFTER_DELETE);
+        final Node expected = this.loadTree(DiffNodeTest.TREE_AFTER_DELETE);
         Assertions.assertTrue(expected.deepCompare(actual));
     }
 
@@ -218,7 +218,7 @@ void testDiffNodeAsString() {
      * @return The file content
      */
     private String getFileContent(final String name) {
-        final String file = DifferenceNodeTest.TESTS_PATH.concat(name);
+        final String file = DiffNodeTest.TESTS_PATH.concat(name);
         boolean oops = false;
         String source = "";
         try {
diff --git a/src/test/java/org/cqfn/astranaut/core/base/PatternNodeTest.java b/src/test/java/org/cqfn/astranaut/core/base/PatternNodeTest.java
index 0ca3868..c77e59a 100644
--- a/src/test/java/org/cqfn/astranaut/core/base/PatternNodeTest.java
+++ b/src/test/java/org/cqfn/astranaut/core/base/PatternNodeTest.java
@@ -61,9 +61,9 @@ public Position getEnd() {
      * Source implementation for test purposes.
      * @since 1.1.5
      */
-    private static class TestSource implements Source {
+    private static final class TestSource implements Source {
         @Override
-        public String getFragmentAsString(Position start, Position end) {
+        public String getFragmentAsString(final Position start, final Position end) {
             return "";
         }
     }
@@ -72,7 +72,7 @@ public String getFragmentAsString(Position start, Position end) {
      * Position implementation for test purposes.
      * @since 1.1.5
      */
-    private static class TestPosition implements Position {
+    private static final class TestPosition implements Position {
         /**
          * Source.
          */
@@ -88,7 +88,7 @@ private static class TestPosition implements Position {
          * @param source Source
          * @param column Column number
          */
-        private TestPosition(final Source source, int column) {
+        private TestPosition(final Source source, final int column) {
             this.source = source;
             this.column = column;
         }