test(compaction): pass the log directory through the fixture constructor

- making location a plain non-static member left manifest_path and
  compaction_catalog_path initialized from the default directory even when a
  derived fixture overrode location in its constructor body (Copilot review)
- add a compaction_test constructor that takes the location so the dependent
  paths are derived from the actual value; offline_compaction_test now passes
  /tmp/offline_compaction_test through it

Author: umegane

test/limestone/compaction/compaction_test_fixture.h

@@ -48,9 +48,12 @@ extern const std::string_view data_nondurable;
 
 class compaction_test : public ::testing::Test {
 public:
-    // Non-static so that derived fixtures can use a distinct directory; sharing one
-    // directory across separate test suites causes a race when ctest runs them in
-    // parallel. Derived fixtures may override this in their constructor.
+    compaction_test() = default;
+    // Derived fixtures pass a distinct directory through this constructor so that the
+    // dependent paths below are derived from the actual location. Sharing one directory
+    // across separate test suites causes a race when ctest runs them in parallel.
+    explicit compaction_test(const char* location) : location(location) {}
+
     const char* location = "/tmp/compaction_test";
     const boost::filesystem::path manifest_path = boost::filesystem::path(location) / std::string(limestone::internal::manifest::file_name);
     const boost::filesystem::path compaction_catalog_path = boost::filesystem::path(location) / "compaction_catalog";

test/limestone/compaction/offline_compaction_test.cpp

@@ -42,7 +42,7 @@ class offline_compaction_test : public compaction_test {
 public:
     // Use a dedicated directory so this suite does not collide with compaction_test,
     // which shares the same fixture base; ctest runs the two suites in parallel.
-    offline_compaction_test() { location = "/tmp/offline_compaction_test"; }
+    offline_compaction_test() : compaction_test("/tmp/offline_compaction_test") {}
 
     // Path to the offline compaction utility (tglogutil), relative to the test
     // executable's working directory. This matches the convention used by