Add test for PrioritySorterJobColumn class (#434)

* Add test for PrioritySorterJobColumn class

* Make ItemInfo method public to allow instantiation from other classes

* Fixed typo

* Revert "Fixed typo"

This reverts commit 9b9cc1e.

* Simplify the test and remove production object change

No need to make the ItemInfo constructor publicly visible when the test
class can be moved into the same package as the ItemInfo class.

---------

Co-authored-by: Mark Waite <[email protected]>

src/test/java/jenkins/advancedqueue/sorter/PrioritySorterJobColumnTest.java

@@ -0,0 +1,61 @@
+package jenkins.advancedqueue.sorter;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+
+import hudson.model.FreeStyleProject;
+import hudson.model.Queue;
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.Calendar;
+import jenkins.advancedqueue.PrioritySorterJobColumn;
+import org.junit.BeforeClass;
+import org.junit.ClassRule;
+import org.junit.Test;
+import org.jvnet.hudson.test.JenkinsRule;
+
+public class PrioritySorterJobColumnTest {
+
+    @ClassRule
+    public static JenkinsRule j = new JenkinsRule();
+
+    private static FreeStyleProject project;
+    private static ItemInfo itemInfo;
+    private static PrioritySorterJobColumn column;
+
+    @BeforeClass
+    public static void setUp() throws IOException {
+        project = j.createFreeStyleProject("test-job");
+        Queue.WaitingItem waitingItem = new Queue.WaitingItem(Calendar.getInstance(), project, new ArrayList<>());
+        itemInfo = new ItemInfo(waitingItem);
+        column = new PrioritySorterJobColumn();
+    }
+
+    @Test
+    public void getPriorityReturnsPendingWhenItemInfoIsNull() throws Exception {
+        assertEquals("Pending", column.getPriority(project));
+    }
+
+    @Test
+    public void getPriorityReturnsCorrectPriority() throws Exception {
+        QueueItemCache.get().addItem(itemInfo);
+        assertEquals("0", column.getPriority(project));
+    }
+
+    @Test
+    public void getPriorityReturnsPendingForNonExistentJob() throws Exception {
+        assertEquals("Pending", column.getPriority(project));
+    }
+
+    @Test
+    public void descriptorImplDisplayNameIsCorrect() {
+        assertEquals("Priority Value", column.getDescriptor().getDisplayName());
+    }
+
+    @Test
+    public void descriptorImplShownByDefaultIsFalse() {
+        PrioritySorterJobColumn.DescriptorImpl descriptor =
+                (PrioritySorterJobColumn.DescriptorImpl) column.getDescriptor();
+        assertFalse(descriptor.shownByDefault());
+    }
+}