no need to constantly restart spark sessions

Author: Robert Kruszewski

sql/core/src/test/java/test/org/apache/spark/sql/JavaDataFrameSuite.java

@@ -45,19 +45,19 @@
 import static org.apache.spark.sql.types.DataTypes.*;
 
 public class JavaDataFrameSuite {
-  private transient TestSparkSession spark;
-  private transient JavaSparkContext jsc;
+  private static TestSparkSession spark;
+  private static JavaSparkContext jsc;
 
-  @Before
-  public void setUp() {
+  @BeforeClass
+  public static void setUp() {
     // Trigger static initializer of TestData
     spark = new TestSparkSession();
     jsc = new JavaSparkContext(spark.sparkContext());
     spark.loadTestData();
   }
 
-  @After
-  public void tearDown() {
+  @AfterClass
+  public static void tearDown() {
     spark.stop();
     spark = null;
   }