Asserts for check

test/aud/exam/prep/list/DoubleListItemProcessorTest.java

@@ -0,0 +1,51 @@
+package aud.exam.prep.list;
+
+import aud.exam.prep.SequenceProcessor;
+import aud.exam.prep.SequenceProcessorTest;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+abstract class DoubleListItemProcessorTest extends SequenceProcessorTest<DoubleListItem<Integer>> {
+
+    protected DoubleListItemProcessorTest(SequenceProcessor<Integer, DoubleListItem<Integer>> processor) {
+        super(processor);
+    }
+
+    @Test
+    void testThat_checkOfNullIsTrue() {
+        assertTrue(processor.check(null));
+    }
+
+    @Test
+    void testThat_checkOfNoKeyIsFalse() {
+        var item = new DoubleListItem<Integer>();
+        assertFalse(processor.check(item));
+    }
+
+    @Test
+    void testThat_checkOfNoPrevOfNextIsFalse() {
+        var item = new DoubleListItem<Integer>();
+        item.key = 1;
+
+        item.next = new DoubleListItem<>();
+        item.next.key = 1;
+
+        assertFalse(processor.check(item));
+    }
+
+    @Test
+    void testThat_checkOfCircleIsFalse() {
+        var item = new DoubleListItem<Integer>();
+        item.next = item;
+        assertFalse(processor.check(item));
+    }
+
+    @Test
+    void testThat_checkPrevNextNotMatchingIsFalse() {
+        var item = new DoubleListItem<Integer>();
+        item.next = new DoubleListItem<>();
+        item.next.prev = new DoubleListItem<>();
+        assertFalse(processor.check(item));
+    }
+}

test/aud/exam/prep/list/RecursiveDoubleListItemProcessorTest.java

@@ -1,8 +1,6 @@
 package aud.exam.prep.list;
 
-import aud.exam.prep.SequenceProcessorTest;
+public class RecursiveDoubleListItemProcessorTest extends DoubleListItemProcessorTest {
-
-class RecursiveDoubleListItemProcessorTest extends SequenceProcessorTest<DoubleListItem<Integer>> {
 
     protected RecursiveDoubleListItemProcessorTest() {
         super(new RecursiveDoubleListItemProcessor<>());