Add checkStructField utility

Makes it easier to check StructFields

Author: cafreeman

R/pkg/inst/tests/test_sparkSQL.R

@@ -19,6 +19,14 @@ library(testthat)
 
 context("SparkSQL functions")
 
+# Utility function for easily checking the values of a StructField
+checkStructField <- function(actual, expectedName, expectedType, expectedNullable) {
+  expect_equal(class(actual), "structField")
+  expect_equal(actual$name(), expectedName)
+  expect_equal(actual$dataType.toString(), expectedType)
+  expect_equal(actual$nullable(), expectedNullable)
+}
+
 # Tests for SparkSQL functions in SparkR
 
 sc <- sparkR.init()
@@ -54,11 +62,8 @@ test_that("infer types", {
                list(type = 'array', elementType = "integer", containsNull = TRUE))
   testStruct <- infer_type(list(a = 1L, b = "2"))
   expect_true(class(testStruct) == "structType")
-  expect_true(length(testStruct$fields()) == 2)
-  testSF <- testStruct$fields()[[1]]
-  expect_true(class(testSF) == "structField")
-  expect_true(testSF$name() == "a")
-  expect_true(testSF$dataType.toString() == "IntegerType")
+  checkStructField(testStruct$fields()[[1]], "a", "IntegerType", TRUE)
+  checkStructField(testStruct$fields()[[2]], "b", "StringType", TRUE)
   e <- new.env()
   assign("a", 1L, envir = e)
   expect_equal(infer_type(e),