1 files changed, 44 insertions, 0 deletions
diff --git a/src/arrow/r/tests/testthat/helper-roundtrip.R b/src/arrow/r/tests/testthat/helper-roundtrip.R
new file mode 100644
index 000000000..80bcb42f1
--- /dev/null
+++ b/src/arrow/r/tests/testthat/helper-roundtrip.R
@@ -0,0 +1,44 @@
+# 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.
+
+expect_array_roundtrip <- function(x, type, as = NULL) {
+  a <- Array$create(x, type = as)
+  expect_equal(a$type, type)
+  expect_identical(length(a), length(x))
+  if (!inherits(type, c("ListType", "LargeListType", "FixedSizeListType"))) {
+    # TODO: revisit how missingness works with ListArrays
+    # R list objects don't handle missingness the same way as other vectors.
+    # Is there some vctrs thing we should do on the roundtrip back to R?
+    expect_as_vector(is.na(a), is.na(x))
+  }
+  roundtrip <- as.vector(a)
+  expect_equal(roundtrip, x, ignore_attr = TRUE)
+  # Make sure the storage mode is the same on roundtrip (esp. integer vs. numeric)
+  expect_identical(typeof(roundtrip), typeof(x))
+
+  if (length(x)) {
+    a_sliced <- a$Slice(1)
+    x_sliced <- x[-1]
+    expect_equal(a_sliced$type, type)
+    expect_identical(length(a_sliced), length(x_sliced))
+    if (!inherits(type, c("ListType", "LargeListType", "FixedSizeListType"))) {
+      expect_as_vector(is.na(a_sliced), is.na(x_sliced))
+    }
+    expect_as_vector(a_sliced, x_sliced, ignore_attr = TRUE)
+  }
+  invisible(a)
+}