Add test for the App, reuse test data from DiffSuite

src/test/scala/uk/co/gresearch/spark/SparkTestSession.scala

@@ -29,6 +29,7 @@ trait SparkTestSession extends SQLHelper {
       .appName("spark test example")
       .config("spark.sql.shuffle.partitions", 2)
       .config("spark.local.dir", ".")
+      .enableHiveSupport()
       .getOrCreate()
   }
 

src/test/scala/uk/co/gresearch/spark/diff/AppSuite.scala

@@ -0,0 +1,55 @@
+/*
+ * Copyright 2023 G-Research
+ *
+ * Licensed 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 uk.co.gresearch.spark.diff
+
+import org.apache.spark.sql.SaveMode
+import org.scalatest.funsuite.AnyFunSuite
+import uk.co.gresearch.spark.SparkTestSession
+
+import java.io.File
+
+
+class AppSuite extends AnyFunSuite with SparkTestSession {
+  import spark.implicits._
+
+  test("run app with file and hive table") {
+    withTempPath { path =>
+      // write left dataframe as csv
+      val leftPath = new File(path, "left.csv").getAbsolutePath
+      DiffSuite.left(spark).write.csv(leftPath)
+
+      // write right dataframe as parquet table
+      DiffSuite.right(spark).write.format("parquet").mode(SaveMode.Overwrite).saveAsTable("right_parquet")
+
+      // launch app
+      val jsonPath = new File(path, "diff.json").getAbsolutePath
+      App.main(Array(
+        "--left-format", "csv",
+        "--left-schema", "id int, value string",
+        "--output-format", "json",
+        "--id", "id",
+        leftPath,
+        "right_parquet",
+        jsonPath
+      ))
+
+      // assert written diff
+      val actual = spark.read.json(jsonPath)
+      assert(actual.orderBy($"id").collect() === DiffSuite.expectedDiff)
+    }
+  }
+}

src/test/scala/uk/co/gresearch/spark/diff/DiffSuite.scala

@@ -19,7 +19,7 @@ package uk.co.gresearch.spark.diff
 import org.apache.spark.sql.functions.regexp_replace
 import org.apache.spark.sql.internal.SQLConf
 import org.apache.spark.sql.types._
-import org.apache.spark.sql.{Dataset, Encoders, Row}
+import org.apache.spark.sql.{Dataset, Encoders, Row, SparkSession}
 import org.scalatest.funsuite.AnyFunSuite
 import uk.co.gresearch.spark.{SparkTestSession, distinctPrefixFor}
 
@@ -93,21 +93,40 @@ case class DiffAsOneSide(diff: String,
                          id: Int,
                          value: Option[String])
 
+object DiffSuite {
+  def left(spark: SparkSession): Dataset[Value] = {
+    import spark.implicits._
+    Seq(
+      Value(1, Some("one")),
+      Value(2, Some("two")),
+      Value(3, Some("three"))
+    ).toDS()
+  }
+
+  def right(spark: SparkSession): Dataset[Value] = {
+    import spark.implicits._
+    Seq(
+      Value(1, Some("one")),
+      Value(2, Some("Two")),
+      Value(4, Some("four"))
+    ).toDS()
+  }
+
+  val expectedDiff: Seq[Row] = Seq(
+    Row("N", 1, "one", "one"),
+    Row("C", 2, "two", "Two"),
+    Row("D", 3, "three", null),
+    Row("I", 4, null, "four")
+  )
+
+}
+
 class DiffSuite extends AnyFunSuite with SparkTestSession {
 
   import spark.implicits._
 
-  lazy val left: Dataset[Value] = Seq(
-    Value(1, Some("one")),
-    Value(2, Some("two")),
-    Value(3, Some("three"))
-  ).toDS()
-
-  lazy val right: Dataset[Value] = Seq(
-    Value(1, Some("one")),
-    Value(2, Some("Two")),
-    Value(4, Some("four"))
-  ).toDS()
+  lazy val left: Dataset[Value] = DiffSuite.left(spark)
+  lazy val right: Dataset[Value] = DiffSuite.right(spark)
 
   lazy val left7: Dataset[Value7] = Seq(
     Value7(1, Some("one"), Some("one label")),
@@ -155,12 +174,7 @@ class DiffSuite extends AnyFunSuite with SparkTestSession {
 
   lazy val expectedDiffColumns: Seq[String] = Seq("diff", "id", "left_value", "right_value")
 
-  lazy val expectedDiff: Seq[Row] = Seq(
-    Row("N", 1, "one", "one"),
-    Row("C", 2, "two", "Two"),
-    Row("D", 3, "three", null),
-    Row("I", 4, null, "four")
-  )
+  lazy val expectedDiff: Seq[Row] = DiffSuite.expectedDiff
 
   lazy val expectedReverseDiff: Seq[Row] = Seq(
     Row("N", 1, "one", "one"),