[SPARK-29725][SQL][TESTS] Add ThriftServerPageSuite

### What changes were proposed in this pull request?
Added UT for the classes `ThriftServerPage.scala` and `ThriftServerSessionPage.scala`

### Why are the changes needed?

Currently, there are no UTs for testing Thriftserver UI page
### Does this PR introduce any user-facing change?

No

### How was this patch tested?

UT

Closes apache#26403 from shahidki31/ut.

Authored-by: shahid <[email protected]>
Signed-off-by: HyukjinKwon <[email protected]>

sql/hive-thriftserver/pom.xml

@@ -120,7 +120,11 @@
       <type>test-jar</type>
       <scope>test</scope>
     </dependency>
-
+    <dependency>
+      <groupId>org.mockito</groupId>
+      <artifactId>mockito-core</artifactId>
+      <scope>test</scope>
+    </dependency>
     <dependency>
       <groupId>net.sf.jpam</groupId>
       <artifactId>jpam</artifactId>

sql/hive-thriftserver/src/test/scala/org/apache/spark/sql/hive/thriftserver/ui/ThriftServerPageSuite.scala

@@ -0,0 +1,95 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.spark.sql.hive.thriftserver.ui
+
+import java.util.Locale
+import javax.servlet.http.HttpServletRequest
+
+import org.mockito.Mockito.{mock, when, RETURNS_SMART_NULLS}
+
+import org.apache.spark.SparkFunSuite
+import org.apache.spark.scheduler.SparkListenerJobStart
+import org.apache.spark.sql.hive.thriftserver.HiveThriftServer2
+import org.apache.spark.sql.hive.thriftserver.HiveThriftServer2.HiveThriftServer2Listener
+import org.apache.spark.sql.internal.SQLConf
+
+class ThriftServerPageSuite extends SparkFunSuite {
+
+  /**
+   * Run a dummy session and return the listener
+   */
+  private def getListener: HiveThriftServer2Listener = {
+    val listener = new HiveThriftServer2Listener(mock(classOf[HiveThriftServer2]), new SQLConf)
+
+    listener.onSessionCreated("localhost", "sessionid", "user")
+    listener.onStatementStart("id", "sessionid", "dummy query", "groupid", "user")
+    listener.onStatementParsed("id", "dummy plan")
+    listener.onJobStart(SparkListenerJobStart(0, System.currentTimeMillis(), Seq()))
+    listener.onStatementFinish("id")
+    listener.onOperationClosed("id")
+    listener.onSessionClosed("sessionid")
+    listener
+  }
+
+  test("thriftserver page should load successfully") {
+    val request = mock(classOf[HttpServletRequest])
+    val tab = mock(classOf[ThriftServerTab], RETURNS_SMART_NULLS)
+    when(tab.listener).thenReturn(getListener)
+    when(tab.appName).thenReturn("testing")
+    when(tab.headerTabs).thenReturn(Seq.empty)
+    val page = new ThriftServerPage(tab)
+    val html = page.render(request).toString().toLowerCase(Locale.ROOT)
+
+    // session statistics and sql statistics tables should load successfully
+    assert(html.contains("session statistics (1)"))
+    assert(html.contains("sql statistics (1)"))
+    assert(html.contains("dummy query"))
+    assert(html.contains("dummy plan"))
+
+    // Pagination support
+    assert(html.contains("<label>1 pages. jump to</label>"))
+
+    // Hiding table support
+    assert(html.contains("class=\"collapse-aggregated-sessionstat" +
+       " collapse-table\" onclick=\"collapsetable"))
+  }
+
+  test("thriftserver session page should load successfully") {
+    val request = mock(classOf[HttpServletRequest])
+    when(request.getParameter("id")).thenReturn("sessionid")
+    val tab = mock(classOf[ThriftServerTab], RETURNS_SMART_NULLS)
+    when(tab.listener).thenReturn(getListener)
+    when(tab.appName).thenReturn("testing")
+    when(tab.headerTabs).thenReturn(Seq.empty)
+    val page = new ThriftServerSessionPage(tab)
+    val html = page.render(request).toString().toLowerCase(Locale.ROOT)
+
+    // session sql statistics table should load successfully
+    assert(html.contains("sql statistics"))
+    assert(html.contains("user"))
+    assert(html.contains("groupid"))
+
+    // Pagination support
+    assert(html.contains("<label>1 pages. jump to</label>"))
+
+    // Hiding table support
+    assert(html.contains("collapse-aggregated-sqlsessionstat collapse-table\"" +
+          " onclick=\"collapsetable"))
+  }
+}
+