Add PrimitiveTypeCustomArrayElementDelimiter test.

cpp/src/arrow/pretty_print_test.cc

@@ -200,6 +200,33 @@ TEST_F(TestPrettyPrint, PrimitiveTypeNoNewlines) {
   CheckPrimitive<Int32Type, int32_t>(options, is_valid, values, expected, false);
 }
 
+TEST_F(TestPrettyPrint, PrimitiveTypeCustomArrayElementDelimiter) {
+  PrettyPrintOptions options{};
+  // Display array contents on one line.
+  options.skip_new_lines = true;
+  // Display maximum of 3 elements at the beginning and at the end of the array
+  options.window = 3;
+  // Use a custom array element delimiter of " | ",
+  // rather than the default delimiter (i.e. ",").
+  options.array_element_delimiter = " | ";
+
+  // Short array without ellipsis
+  {
+      std::vector<bool> is_valid = {true, true, false, true, false};
+      std::vector<int32_t> values = {1, 2, 3, 4, 5};
+      const char* expected = "[1 | 2 | null | 4 | null]";
+      CheckPrimitive<Int32Type, int32_t>(options, is_valid, values, expected, false);
+  }
+
+  // Longer array with ellipsis
+  {
+      std::vector<bool> is_valid = {true, false, true, true, false, true, false, true, true};
+      std::vector<int32_t> values = {1, 2, 3, 4, 5, 6, 7, 8, 9};
+      const char* expected = "[1 | null | 3 | ... | null | 8 | 9]";
+      CheckPrimitive<Int32Type, int32_t>(options, is_valid, values, expected, false);
+  }
+}
+
 TEST_F(TestPrettyPrint, Int8) {
   static const char* expected = R"expected([
   0,