From 9d02c7977c92754259cc29aa78e809e8ff8d4e73 Mon Sep 17 00:00:00 2001
From: Shan Zhou <11672456+Shan-Zhou@users.noreply.github.com>
Date: Sun, 13 Sep 2026 16:59:00 +0900
Subject: [PATCH] test: eliminate race conditions and fix flaky tailing tests
 with WaitForLines

---
 .../DebugViewppTest/DebugView++Test.cpp       | 54 +++++++++++++------
 1 file changed, 39 insertions(+), 15 deletions(-)

diff --git a/application/DebugViewppTest/DebugView++Test.cpp b/application/DebugViewppTest/DebugView++Test.cpp
index 9e80f604..552d5159 100644
--- a/application/DebugViewppTest/DebugView++Test.cpp
+++ b/application/DebugViewppTest/DebugView++Test.cpp
@@ -620,6 +620,31 @@ void RemoveLinesFromFile(const std::string& filename, int linesToRemove)
     Win32::HFile(GetTestFileName()).resize(offset);
 }
 
+Lines WaitForLines(ActiveExecutorClient& executor, LogSources& logsources, size_t expectedCount,
+                   std::chrono::milliseconds timeout = std::chrono::milliseconds(2000),
+                   std::chrono::milliseconds interval = std::chrono::milliseconds(50))
+{
+    Lines accumulated;
+    const auto startTime = std::chrono::steady_clock::now();
+    while (accumulated.size() < expectedCount)
+    {
+        Lines batch;
+        executor.Call([&] { batch = logsources.GetLines(); });
+        accumulated.insert(accumulated.end(),
+                           std::make_move_iterator(batch.begin()),
+                           std::make_move_iterator(batch.end()));
+
+        if (accumulated.size() >= expectedCount)
+            break;
+
+        if (std::chrono::steady_clock::now() - startTime >= timeout)
+            break;
+
+        std::this_thread::sleep_for(interval);
+    }
+    return accumulated;
+}
+
 BOOST_AUTO_TEST_CASE(LogSourceAnyFileReader)
 {
     using namespace std::chrono_literals;
@@ -628,10 +653,8 @@ BOOST_AUTO_TEST_CASE(LogSourceAnyFileReader)
     auto filename = CreateTestFile();
     executor->Call([&] { logsources.SetAutoNewLine(true); });
     executor->Call([&] { logsources.AddAnyFileReader(WStr(filename), true); });
-    std::this_thread::sleep_for(200ms);
 
-    Lines lines;
-    executor->Call([&] { lines = logsources.GetLines(); });
+    auto lines = WaitForLines(*executor, logsources, 5);
     BOOST_TEST(lines.size() == 5);
 }
 
@@ -643,20 +666,24 @@ BOOST_AUTO_TEST_CASE(LogSourceAnyFileReaderResychronizeShrinkingFile)
     auto filename = CreateTestFile();
     executor->Call([&] { logsources.SetAutoNewLine(true); });
     executor->Call([&] { logsources.AddAnyFileReader(WStr(filename), true); });
-    std::this_thread::sleep_for(200ms);
 
-    Lines lines;
-    executor->Call([&] { lines = logsources.GetLines(); });
+    auto lines = WaitForLines(*executor, logsources, 5);
     BOOST_TEST(lines.size() == 5);
 
     RemoveLinesFromFile(GetTestFileName(), 2);
+    auto shrinkLines = WaitForLines(*executor, logsources, 1);
+    BOOST_TEST(shrinkLines.size() == 1);
+    if (!shrinkLines.empty())
+    {
+        BOOST_TEST(shrinkLines.at(0).message.find("file shrank") != std::string::npos);
+    }
+
     AppendToTestFile();
     AppendToTestFile();
     AppendToTestFile();
 
-    std::this_thread::sleep_for(200ms);
-    executor->Call([&] { lines = logsources.GetLines(); });
-    BOOST_TEST(lines.size() == 4);
+    auto appendLines = WaitForLines(*executor, logsources, 3);
+    BOOST_TEST(appendLines.size() == 3);
 }
 
 std::string GetTestFileAsString()
@@ -737,11 +764,9 @@ BOOST_AUTO_TEST_CASE(LogSourceAnyFileReaderEmptyLines)
     auto filename = CreateAsciiTestFile();
     executor->Call([&] { logsources.SetAutoNewLine(true); });
     executor->Call([&] { logsources.AddAnyFileReader(WStr(filename), true); });
-    std::this_thread::sleep_for(200ms);
 
     {
-        Lines lines;
-        executor->Call([&] { lines = logsources.GetLines(); });
+        auto lines = WaitForLines(*executor, logsources, 4);
         BOOST_TEST(lines.size() == 4);
         BOOST_TEST(lines.at(0).message.find("tailing") != std::string::npos);
         BOOST_TEST(lines.at(1).message.find("first") != std::string::npos);
@@ -766,9 +791,8 @@ BOOST_AUTO_TEST_CASE(LogSourceLoopbackOrdering)
     executor->Call([&] { logsources.AddMessage("Loopback message 2"); });
     executor->Call([&] { logsources.AddMessage("Loopback message 3"); });
     executor->Call([&] { logsources.AddAnyFileReader(WStr(filename), true); });
-    std::this_thread::sleep_for(200ms);
-    Lines lines;
-    executor->Call([&] { lines = logsources.GetLines(); });
+
+    auto lines = WaitForLines(*executor, logsources, 7);
 
     BOOST_TEST(lines.at(0).message == "Loopback message 1");
     BOOST_TEST(lines.at(1).message == "Loopback message 2");