diff --git a/pw_preprocessor/concat_test.cc b/pw_preprocessor/concat_test.cc
new file mode 100644
index 0000000..cd3af3a
--- /dev/null
+++ b/pw_preprocessor/concat_test.cc
@@ -0,0 +1,86 @@
+// Copyright 2019 The Pigweed Authors
+//
+// 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
+//
+//     https://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.
+
+#include "pw_preprocessor/concat.h"
+
+#include "pw_preprocessor/util.h"
+#include "pw_unit_test/framework.h"
+
+namespace pw {
+namespace {
+
+TEST(Concat, WithoutMacroExpansions) {
+  static_assert(PW_CONCAT() 9000 PW_CONCAT() == 9000);
+  static_assert(PW_CONCAT(1, 2) == 12);
+  static_assert(PW_CONCAT(1, 2, 3, 4) == 1234);
+  static_assert(PW_CONCAT(1, 2, 3, 4, 5) == 12345);
+  static_assert(PW_CONCAT(1, 2, 3, 4, 5, 6) == 123456);
+  static_assert(PW_CONCAT(1, 2, 3, 4, 5, 6, 7) == 1234567);
+  static_assert(PW_CONCAT(1, 2, 3, 4, 5, 6, 7, 8) == 12345678);
+
+  static_assert(PW_CONCAT(0x, 3, 4, 5, 6, 7, 8, llu) == 0x345678llu);
+  static_assert(PW_CONCAT(0x, 3, 4, 5, 6, 7, 8, 9, llu) == 0x3456789llu);
+  static_assert(PW_CONCAT(0x, 3, 4, 5, 6, 7, 8, 9, A, llu) == 0x3456789Allu);
+  static_assert(PW_CONCAT(0x, 3, 4, 5, 6, 7, 8, 9, A, B, llu) ==
+                0x3456789ABllu);
+  static_assert(PW_CONCAT(0x, 3, 4, 5, 6, 7, 8, 9, A, B, C, llu) ==
+                0x3456789ABCllu);
+  static_assert(PW_CONCAT(0x, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, llu) ==
+                0x3456789ABCDllu);
+  static_assert(PW_CONCAT(0x, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, llu) ==
+                0x3456789ABCDEllu);
+  static_assert(PW_CONCAT(0x, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, F, llu) ==
+                0x3456789ABCDEFllu);
+  static_assert(PW_CONCAT(0x, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, F, F, llu) ==
+                0x3456789ABCDEFFllu);
+}
+
+// Macros which expand out to test that PW_CONCAT properly expands them.
+#define _PW_TEST_SECTION(x) "section: " x
+#define _PW_TEST_NUMBER 123
+#define _PW_OUTER_MACRO(section_name) \
+  _PW_TEST_SECTION(PW_STRINGIFY(PW_CONCAT(section_name, _PW_TEST_NUMBER)))
+
+#define _PW_WHOSE() my
+#define _PW_WHAT var
+
+TEST(Concat, WithMacroExpansions) {
+  static_assert(PW_CONCAT(_PW_TEST_NUMBER, 5) == 1235);
+
+  int my_var;
+  EXPECT_EQ(&PW_CONCAT(_PW_WHOSE(), _, _PW_WHAT), &my_var);
+
+  EXPECT_STREQ(_PW_OUTER_MACRO(what is up), "section: what is up123");
+}
+
+// Test concatenation up to the maximum supported length.
+TEST(Concat, MaximumConcatenationLength) {
+  constexpr int value31_234567890123456789012345678901 = 1337;
+  constexpr int value32_2345678901234567890123456789012 = 101010;
+
+  // clang-format off
+  static_assert(PW_CONCAT(value31_, 2, 3, 4, 5, 6, 7, 8, 9, 0,
+                                 1, 2, 3, 4, 5, 6, 7, 8, 9, 0,
+                                 1, 2, 3, 4, 5, 6, 7, 8, 9, 0,
+                                 1) == 1337);
+
+  static_assert(PW_CONCAT(value32_, 2, 3, 4, 5, 6, 7, 8, 9, 0,
+                                 1, 2, 3, 4, 5, 6, 7, 8, 9, 0,
+                                 1, 2, 3, 4, 5, 6, 7, 8, 9, 0,
+                                 1, 2) == 101010);
+  // clang-format on
+}
+
+}  // namespace
+}  // namespace pw