test_utils: utility for getting a test directory

This adds a utility method to get the pathname for a directory that
should be uniquely used by a single test case iteration.

src/v/test_utils/CMakeLists.txt

@@ -7,7 +7,9 @@ find_package(GTest)
 
 v_cc_library(
   NAME gtest_main
-  SRCS gtest_main.cc
+  SRCS
+    gtest_main.cc
+    gtest_utils.cc
   DEPS Seastar::seastar Seastar::seastar_testing GTest::gtest GTest::gmock v::bytes_random)
 
 add_subdirectory(tests)

src/v/test_utils/gtest_main.cc

@@ -8,12 +8,16 @@
  * the Business Source License, use of this software will be governed
  * by the Apache License, Version 2.0
  */
+#include "test_utils/gtest_utils.h"
 #include "test_utils/test.h"
 
 int main(int argc, char** argv) {
     testing::InitGoogleTest(&argc, argv);
     GTEST_FLAG_SET(death_test_style, "threadsafe");
 
+    auto& listeners = ::testing::UnitTest::GetInstance()->listeners();
+    listeners.Append(new rp_test_listener());
+
     /*
      * if the test is being passed --gtest_list_tests then do not start Seastar.
      * this is an important optimization for using `gtest_discover_tests`

src/v/test_utils/gtest_utils.cc

@@ -0,0 +1,52 @@
+/*
+ * Copyright 2024 Redpanda Data, Inc.
+ *
+ * Use of this software is governed by the Business Source License
+ * included in the file licenses/BSL.md
+ *
+ * As of the Change Date specified in that file, in accordance with
+ * the Business Source License, use of this software will be governed
+ * by the Apache License, Version 2.0
+ */
+#include "test_utils/gtest_utils.h"
+
+#include "base/vassert.h"
+#include "random/generators.h"
+
+#include <seastar/core/lowres_clock.hh>
+
+#include <fmt/format.h>
+#include <gtest/gtest.h>
+
+namespace {
+int gtest_iteration = 0;
+} // anonymous namespace
+
+void rp_test_listener::OnTestIterationStart(
+  const ::testing::UnitTest& /*unit_test*/, int iteration) {
+    gtest_iteration = iteration;
+}
+
+ss::sstring get_test_directory() {
+    const auto* test_info
+      = ::testing::UnitTest::GetInstance()->current_test_info();
+    vassert(test_info != nullptr, "Must be a gtest!");
+
+    // The current timestamp uniquely identifies the process' test incantation,
+    // and the test iteration uniquely identifies the individual runs of test
+    // cases, e.g. in case of --gtest_repeat.
+    //
+    // This allows repeated test runs to operate independently without worrying
+    // about leftover files from previous iterations.
+    static auto now = ss::lowres_clock::now();
+    ss::sstring dir = fmt::format(
+      "{}.{}.{}.{}",
+      test_info->test_suite_name(),
+      test_info->name(),
+      now.time_since_epoch().count(),
+      gtest_iteration);
+
+    // Swap out any '/'s (may come from parameterized tests).
+    std::replace(dir.begin(), dir.end(), '/', '_');
+    return dir;
+}

src/v/test_utils/gtest_utils.h

@@ -0,0 +1,41 @@
+/*
+ * Copyright 2024 Redpanda Data, Inc.
+ *
+ * Use of this software is governed by the Business Source License
+ * included in the file licenses/BSL.md
+ *
+ * As of the Change Date specified in that file, in accordance with
+ * the Business Source License, use of this software will be governed
+ * by the Apache License, Version 2.0
+ */
+#pragma once
+
+#include "base/seastarx.h"
+
+#include <seastar/core/seastar.hh>
+
+#include <gtest/gtest.h>
+
+// Listens to the start of a gtest test iteration. May be used to track the
+// test iteration number.
+class rp_test_listener : public ::testing::EmptyTestEventListener {
+    void
+    OnTestIterationStart(const ::testing::UnitTest&, int iteration) override;
+};
+
+// Returns a pathname that may be used for the currently running test.
+// Expects that the caller is in the context of a GTest.
+//
+// Relies on callers to create the directory.
+//
+// Examples:
+//
+// clang-format off
+// MySeastarFixture.TestGetTestDirectory.6125307633855650.4
+// ^-- test suite   ^-- test case        ^-- timestamp    ^-- iteration
+//
+// Divisible_MySeastarParamFixture.TestGetTestDirectory_0.6126774487959615.6
+// ^-- parameter name                                   ^-- parameter      ^-- iteration
+//           ^-- test suite        ^-- test case          ^-- timestamp
+// clang-format on
+ss::sstring get_test_directory();

src/v/test_utils/tests/gtest_test.cc

@@ -9,9 +9,15 @@
  * by the Apache License, Version 2.0
  */
 #include "test_utils/async.h"
+#include "test_utils/gtest_utils.h"
 #include "test_utils/test.h"
 
+#include <seastar/core/seastar.hh>
 #include <seastar/core/sleep.hh>
+#include <seastar/util/defer.hh>
+#include <seastar/util/file.hh>
+
+#include <gtest/gtest.h>
 
 #include <chrono>
 
@@ -163,3 +169,36 @@ TEST_P(NotSeastarFixtureParam, T) {}
 
 INSTANTIATE_TEST_SUITE_P(
   NotSeastarParamTest, NotSeastarFixtureParam, testing::Values(1, 2, 3));
+
+class directory_test {
+public:
+    // Test body that creates and removes a test directory.
+    // Encapsulated to be reused across different test harness types.
+    void create_and_remove() {
+        auto dir = get_test_directory();
+        auto dir_again = get_test_directory();
+
+        // Repeated calls to get_test_directory() from the same test process
+        // should result in the same output.
+        ASSERT_EQ(dir, dir_again);
+
+        ASSERT_FALSE(ss::file_exists(dir).get());
+        ss::recursive_touch_directory(dir).get();
+        auto cleanup = ss::defer([&dir] {
+            ss::recursive_remove_directory(std::filesystem::path{dir}).get();
+        });
+        ASSERT_TRUE(ss::file_exists(dir).get());
+    }
+};
+
+TEST(NotSeastar, TestGetTestDirectory) {
+    ASSERT_NO_FATAL_FAILURE(directory_test{}.create_and_remove());
+}
+
+TEST_F(MySeastarFixture, TestGetTestDirectory) {
+    ASSERT_NO_FATAL_FAILURE(directory_test{}.create_and_remove());
+}
+
+TEST_P(MySeastarParamFixture, TestGetTestDirectory) {
+    ASSERT_NO_FATAL_FAILURE(directory_test{}.create_and_remove());
+}