[SPARK-16027][SPARKR] Fix R tests SparkSession init/stop

## What changes were proposed in this pull request?

Fix R SparkSession init/stop, and warnings of reusing existing Spark Context

## How was this patch tested?

unit tests

shivaram

Author: Felix Cheung <felixcheung_m@hotmail.com>

Closes #14177 from felixcheung/rsessiontest.

1 files changed, 10 insertions, 13 deletions

diff --git a/R/pkg/inst/tests/testthat/test_context.R b/R/pkg/inst/tests/testthat/test_context.R
index 2a1bd61b11..8bd134a58d 100644
--- a/R/pkg/inst/tests/testthat/test_context.R
+++ b/R/pkg/inst/tests/testthat/test_context.R
@@ -63,18 +63,14 @@ test_that("repeatedly starting and stopping SparkR", {
   }
 })
 
-# Does not work consistently even with Hive off
-# nolint start
-# test_that("repeatedly starting and stopping SparkR", {
-#   for (i in 1:4) {
-#     sparkR.session(enableHiveSupport = FALSE)
-#     df <- createDataFrame(data.frame(dummy=1:i))
-#     expect_equal(count(df), i)
-#     sparkR.session.stop()
-#     Sys.sleep(5) # Need more time to shutdown Hive metastore
-#   }
-# })
-# nolint end
+test_that("repeatedly starting and stopping SparkSession", {
+  for (i in 1:4) {
+    sparkR.session(enableHiveSupport = FALSE)
+    df <- createDataFrame(data.frame(dummy = 1:i))
+    expect_equal(count(df), i)
+    sparkR.session.stop()
+  }
+})
 
 test_that("rdd GC across sparkR.stop", {
   sc <- sparkR.sparkContext() # sc should get id 0
@@ -96,6 +92,7 @@ test_that("rdd GC across sparkR.stop", {
 
   count(rdd3)
   count(rdd4)
+  sparkR.session.stop()
 })
 
 test_that("job group functions can be called", {
@@ -164,7 +161,7 @@ test_that("sparkJars sparkPackages as comma-separated strings", {
 })
 
 test_that("spark.lapply should perform simple transforms", {
-  sc <- sparkR.sparkContext()
+  sparkR.sparkContext()
   doubled <- spark.lapply(1:10, function(x) { 2 * x })
   expect_equal(doubled, as.list(2 * 1:10))
   sparkR.session.stop()