crash_tracker/test: validate file cleanup

Implement a simple test to verify that crash reports are getting removed
on `start()` when their number exceeds `crash_files_to_keep`.

src/v/crash_tracker/recorder.cc

@@ -37,6 +37,8 @@ recorder& get_recorder() {
     return inst;
 }
 
+recorder get_test_recorder() { return recorder{}; }
+
 ss::future<> recorder::ensure_crashdir_exists() const {
     auto crash_report_dir = config::node().crash_report_dir_path();
     if (!co_await ss::file_exists(crash_report_dir.string())) {

src/v/crash_tracker/recorder.h

@@ -41,6 +41,9 @@ class recorder {
     using include_malformed_files
       = ss::bool_class<struct include_malformed_files_tag>;
 
+    /// Visible for testing
+    ~recorder() = default;
+
     ss::future<> start();
     ss::future<> stop();
 
@@ -56,7 +59,6 @@ class recorder {
 
 private:
     recorder() = default;
-    ~recorder() = default;
 
     ss::future<> ensure_crashdir_exists() const;
     ss::future<std::filesystem::path> generate_crashfile_name() const;
@@ -65,9 +67,13 @@ class recorder {
     prepared_writer _writer;
 
     friend recorder& get_recorder();
+    friend recorder get_test_recorder();
 };
 
 /// Singleton access to global static recorder
 recorder& get_recorder();
 
+/// Make a test instance of the recorder that is not a static singleton
+recorder get_test_recorder();
+
 } // namespace crash_tracker

src/v/crash_tracker/tests/BUILD

@@ -16,6 +16,21 @@ redpanda_cc_gtest(
     ],
 )
 
+redpanda_cc_gtest(
+    name = "recorder_test",
+    timeout = "short",
+    srcs = [
+        "recorder_test.cc",
+    ],
+    deps = [
+        "//src/v/config",
+        "//src/v/crash_tracker",
+        "//src/v/model",
+        "//src/v/test_utils:gtest",
+        "@googletest//:gtest",
+    ],
+)
+
 redpanda_cc_binary(
     name = "crash_report_generator",
     srcs = ["report_generator.cc"],

src/v/crash_tracker/tests/CMakeLists.txt

@@ -8,6 +8,16 @@ rp_test(
   ARGS "-- -c 1"
 )
 
+rp_test(
+  UNIT_TEST
+  GTEST
+  BINARY_NAME recorder_test
+  SOURCES
+    recorder_test.cc
+  LIBRARIES v::gtest_main v::config v::crash_tracker
+  ARGS "-- -c 1"
+)
+
 add_executable(crash_report_generator report_generator.cc)
 set_property(TARGET crash_report_generator PROPERTY POSITION_INDEPENDENT_CODE ON)
 target_link_libraries(crash_report_generator PUBLIC v::crash_tracker)

src/v/crash_tracker/tests/recorder_test.cc

@@ -0,0 +1,58 @@
+/*
+ * Copyright 2025 Redpanda Data, Inc.
+ *
+ * Licensed as a Redpanda Enterprise file under the Redpanda Community
+ * License (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * https://github.com/redpanda-data/redpanda/blob/master/licenses/rcl.md
+ */
+
+#include "config/node_config.h"
+#include "crash_tracker/recorder.h"
+#include "test_utils/tmp_dir.h"
+
+#include <gtest/gtest.h>
+
+#include <exception>
+#include <stdexcept>
+
+namespace crash_tracker {
+
+class RecorderTest : public testing::Test {
+public:
+    void SetUp() override {
+        config::node().data_directory.set_value(_dir.get_path());
+    }
+    void TearDown() override {
+        _dir.remove().get();
+        config::node().data_directory.reset();
+    }
+
+private:
+    temporary_dir _dir{"recorder_test"};
+};
+
+TEST_F(RecorderTest, TestFileCleanup) {
+    const auto test_eptr = std::make_exception_ptr(std::runtime_error{""});
+
+    // Observe no recorded crashes before the first start
+    auto crashes = get_test_recorder().get_recorded_crashes().get();
+    ASSERT_EQ(crashes.size(), 0);
+
+    // Simulate lots of crashed restarts to generate crash reports on disk
+    for (size_t i = 0; i < recorder::crash_files_to_keep + 5; i++) {
+        auto rec = get_test_recorder();
+        rec.start().get();
+        rec.record_crash_exception(test_eptr);
+    }
+
+    // Run one more restart and observe that old crash files are cleaned up
+    auto rec = get_test_recorder();
+    rec.start().get();
+
+    crashes = rec.get_recorded_crashes().get();
+    ASSERT_EQ(crashes.size(), recorder::crash_files_to_keep);
+}
+
+} // namespace crash_tracker