[SPARK-22308] Support alternative unit testing styles in external applications

core/src/test/scala/org/apache/spark/SharedSparkContext.scala

@@ -29,10 +29,23 @@ trait SharedSparkContext extends BeforeAndAfterAll with BeforeAndAfterEach { sel
 
   var conf = new SparkConf(false)
 
+  /**
+   * Initialize the [[SparkContext]].  Generally, this is just called from beforeAll; however, in
+   * test using styles other than FunSuite, there is often code that relies on the session between
+   * test group constructs and the actual tests, which may need this session.  It is purely a
+   * semantic difference, but semantically, it makes more sense to call 'initializeContext' between
+   * a 'describe' and an 'it' call than it does to call 'beforeAll'.
+   */
+  protected def initializeContext(): Unit = {
+    if (null == _sc) {
+      _sc = new SparkContext(
+        "local[4]", "test", conf.set("spark.hadoop.fs.file.impl", classOf[DebugFilesystem].getName))
+    }
+  }
+
   override def beforeAll() {
     super.beforeAll()
-    _sc = new SparkContext(
-      "local[4]", "test", conf.set("spark.hadoop.fs.file.impl", classOf[DebugFilesystem].getName))
+    initializeContext()
   }
 
   override def afterAll() {

sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/plans/PlanTest.scala

@@ -17,6 +17,8 @@
 
 package org.apache.spark.sql.catalyst.plans
 
+import org.scalatest.Suite
+
 import org.apache.spark.SparkFunSuite
 import org.apache.spark.sql.AnalysisException
 import org.apache.spark.sql.catalyst.analysis.SimpleAnalyzer
@@ -29,7 +31,13 @@ import org.apache.spark.sql.internal.SQLConf
 /**
  * Provides helper methods for comparing plans.
  */
-trait PlanTest extends SparkFunSuite with PredicateHelper {
+trait PlanTest extends SparkFunSuite with PlanTestBase
+
+/**
+ * Provides helper methods for comparing plans, but without the overhead of
+ * mandating a FunSuite.
+ */
+trait PlanTestBase extends PredicateHelper { self: Suite =>
 
   // TODO(gatorsmile): remove this from PlanTest and all the analyzer rules
   protected def conf = SQLConf.get

sql/core/src/test/scala/org/apache/spark/sql/test/GenericFlatSpecSuite.scala

@@ -0,0 +1,45 @@
+/*
+ * 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.test
+
+import org.scalatest.FlatSpec
+
+/**
+ * The purpose of this suite is to make sure that generic FlatSpec-based scala
+ * tests work with a shared spark session
+ */
+class GenericFlatSpecSuite extends FlatSpec with SharedSparkSession {
+  import testImplicits._
+  initializeSession()
+  val ds = Seq((1, 1), (2, 1), (3, 2), (4, 2), (5, 3), (6, 3), (7, 4), (8, 4)).toDS
+
+  "A Simple Dataset" should "have the specified number of elements" in {
+    assert(8 === ds.count)
+  }
+  it should "have the specified number of unique elements" in {
+      assert(8 === ds.distinct.count)
+  }
+  it should "have the specified number of elements in each column" in {
+    assert(8 === ds.select("_1").count)
+    assert(8 === ds.select("_2").count)
+  }
+  it should "have the correct number of distinct elements in each column" in {
+    assert(8 === ds.select("_1").distinct.count)
+    assert(4 === ds.select("_2").distinct.count)
+  }
+}

sql/core/src/test/scala/org/apache/spark/sql/test/GenericFunSpecSuite.scala

@@ -0,0 +1,47 @@
+/*
+ * 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.test
+
+import org.scalatest.FunSpec
+
+/**
+ * The purpose of this suite is to make sure that generic FunSpec-based scala
+ * tests work with a shared spark session
+ */
+class GenericFunSpecSuite extends FunSpec with SharedSparkSession {
+  import testImplicits._
+  initializeSession()
+  val ds = Seq((1, 1), (2, 1), (3, 2), (4, 2), (5, 3), (6, 3), (7, 4), (8, 4)).toDS
+
+  describe("Simple Dataset") {
+    it("should have the specified number of elements") {
+      assert(8 === ds.count)
+    }
+    it("should have the specified number of unique elements") {
+      assert(8 === ds.distinct.count)
+    }
+    it("should have the specified number of elements in each column") {
+      assert(8 === ds.select("_1").count)
+      assert(8 === ds.select("_2").count)
+    }
+    it("should have the correct number of distinct elements in each column") {
+      assert(8 === ds.select("_1").distinct.count)
+      assert(4 === ds.select("_2").distinct.count)
+    }
+  }
+}

sql/core/src/test/scala/org/apache/spark/sql/test/GenericWordSpecSuite.scala

@@ -0,0 +1,51 @@
+/*
+ * 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.test
+
+import org.scalatest.WordSpec
+
+/**
+ * The purpose of this suite is to make sure that generic WordSpec-based scala
+ * tests work with a shared spark session
+ */
+class GenericWordSpecSuite extends WordSpec with SharedSparkSession {
+  import testImplicits._
+  initializeSession()
+  val ds = Seq((1, 1), (2, 1), (3, 2), (4, 2), (5, 3), (6, 3), (7, 4), (8, 4)).toDS
+
+  "A Simple Dataset" when {
+    "looked at as complete rows" should {
+      "have the specified number of elements" in {
+        assert(8 === ds.count)
+      }
+      "have the specified number of unique elements" in {
+        assert(8 === ds.distinct.count)
+      }
+    }
+    "refined to specific columns" should {
+      "have the specified number of elements in each column" in {
+        assert(8 === ds.select("_1").count)
+        assert(8 === ds.select("_2").count)
+      }
+      "have the correct number of distinct elements in each column" in {
+        assert(8 === ds.select("_1").distinct.count)
+        assert(4 === ds.select("_2").distinct.count)
+      }
+    }
+  }
+}