Tree center tests

Author: williamfiset

com/williamfiset/algorithms/graphtheory/treealgorithms/TreeCenter.java

@@ -3,15 +3,16 @@
  *
  * <p>Time complexity: O(V+E)
  *
- * @author Jeffrey Xiao, https://github.com/jeffrey-xiao
+ * @author Original author: Jeffrey Xiao, https://github.com/jeffrey-xiao
+ * @author Modifications by: William Fiset, william.alexandre.fiset@gmail.com
  */
 package com.williamfiset.algorithms.graphtheory.treealgorithms;
 
 import java.util.ArrayList;
 import java.util.LinkedList;
 import java.util.List;
 
-class TreeCenter {
+public class TreeCenter {
 
   public static List<Integer> findTreeCenters(List<List<Integer>> tree) {
     final int n = tree.size();

javatests/com/williamfiset/algorithms/graphtheory/treealgorithms/TreeCenterTest.java

@@ -0,0 +1,77 @@
+// To run this test in isolation from root folder:
+//
+// $ gradle test --tests
+// javatests.com.williamfiset.algorithms.graphtheory.treealgorithms.TreeCenterTest
+
+package javatests.com.williamfiset.algorithms.graphtheory.treealgorithms;
+
+import static com.google.common.truth.Truth.assertThat;
+import static com.williamfiset.algorithms.graphtheory.treealgorithms.TreeCenter.addUndirectedEdge;
+import static com.williamfiset.algorithms.graphtheory.treealgorithms.TreeCenter.createEmptyTree;
+import static com.williamfiset.algorithms.graphtheory.treealgorithms.TreeCenter.findTreeCenters;
+
+import java.util.*;
+import org.junit.*;
+
+public class TreeCenterTest {
+
+  @Test
+  public void emptyTreeThrowsException() {
+    assertThat(createEmptyTree(0)).isEmpty();
+  }
+
+  @Test
+  public void simpleTest1() {
+    List<List<Integer>> graph = createEmptyTree(9);
+    addUndirectedEdge(graph, 0, 1);
+    addUndirectedEdge(graph, 2, 1);
+    addUndirectedEdge(graph, 2, 3);
+    addUndirectedEdge(graph, 3, 4);
+    addUndirectedEdge(graph, 5, 3);
+    addUndirectedEdge(graph, 2, 6);
+    addUndirectedEdge(graph, 6, 7);
+    addUndirectedEdge(graph, 6, 8);
+    assertThat(findTreeCenters(graph)).containsExactly(2);
+  }
+
+  @Test
+  public void singleton() {
+    assertThat(findTreeCenters(createEmptyTree(1))).containsExactly(0);
+  }
+
+  @Test
+  public void twoNodeTree() {
+    List<List<Integer>> graph = createEmptyTree(2);
+    addUndirectedEdge(graph, 0, 1);
+    assertThat(findTreeCenters(graph)).containsExactly(0, 1);
+  }
+
+  @Test
+  public void simpleTest2() {
+    List<List<Integer>> graph = createEmptyTree(3);
+    addUndirectedEdge(graph, 0, 1);
+    addUndirectedEdge(graph, 1, 2);
+    assertThat(findTreeCenters(graph)).containsExactly(1);
+  }
+
+  @Test
+  public void simpleTest3() {
+    List<List<Integer>> graph = createEmptyTree(4);
+    addUndirectedEdge(graph, 0, 1);
+    addUndirectedEdge(graph, 1, 2);
+    addUndirectedEdge(graph, 2, 3);
+    assertThat(findTreeCenters(graph)).containsExactly(1, 2);
+  }
+
+  @Test
+  public void simpleTest4() {
+    List<List<Integer>> graph = createEmptyTree(7);
+    addUndirectedEdge(graph, 0, 1);
+    addUndirectedEdge(graph, 1, 2);
+    addUndirectedEdge(graph, 2, 3);
+    addUndirectedEdge(graph, 3, 4);
+    addUndirectedEdge(graph, 4, 5);
+    addUndirectedEdge(graph, 4, 6);
+    assertThat(findTreeCenters(graph)).containsExactly(2, 3);
+  }
+}