Tests: live stills with the image buffer full during the pre-pass

Forty frames are all there before the pre-pass ends, with twelve slots in the
image buffer. The collection does not deadlock and the end message goes out. The
frames that found no free slot are not written; the collection reports them:
images_collected stays at forty, images_sent (in the status and in the end
message) counts only the frames written and analysed, and the writer-queue-full
warning is set exactly when frames were lost. Efficiency stays 1.0, as every
frame was received.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01HVeDQsU5a8AJUdJPgWevAK

tests/JFJochReceiverRugnuxTest.cpp

@@ -543,6 +543,50 @@ TEST_CASE("JFJochReceiverRugnux_Stills_ZMQWriterDown", "[JFJochReceiverRugnux]")
     REQUIRE_NOTHROW(writer_future.get());
 }
 
+TEST_CASE("JFJochReceiverRugnux_Stills_BufferFullDuringPrePass", "[JFJochReceiverRugnux]") {
+    // Forty frames, all there before the pre-pass ends, and twelve slots in the image buffer.
+    Logger logger(Catch::getResultCapture().getCurrentTestName());
+    RegisterHDF5Filter();
+
+    const int64_t images = 40;
+    DiffractionExperiment x = StillsExperiment(images);
+    PixelMask mask(x);
+    Stream stream(x, images);
+    stream.Frames(0, images);
+    stream.End();
+
+    const size_t buffer_MiB = 12 * x.GetImageBufferLocationSize() / (1024 * 1024) + 1;
+
+    RecordingPusher pusher;
+    AcquisitionDeviceGroup group;
+    JFJochReceiverService service(group, logger, pusher, buffer_MiB);
+    service.NumThreads(2);
+    service.Indexing(x.GetIndexingSettings());
+    service.RugnuxLive(true, nullptr, 4, 60);
+
+    service.Start(x, mask, nullptr, stream.puller);
+    const auto out = service.Stop();
+
+    // No deadlock, and the end message goes out.
+    CHECK(!out.status.cancelled);
+    CHECK(pusher.Events() == std::vector<std::string>{"start", "image", "end"});
+
+    // A frame that finds no free slot is not written, and the collection says so.
+    CHECK(out.status.images_collected == images);
+    CHECK(out.efficiency == 1.0f);
+    CHECK(out.writer_queue_full_warning == (out.status.images_sent < images));
+    CHECK(out.scan_result.images.size() == out.status.images_sent);
+    REQUIRE(pusher.End());
+    CHECK(pusher.End()->images_collected_count == images);
+    CHECK(pusher.End()->images_sent_to_write_count == out.status.images_sent);
+    CHECK(pusher.Images().size() == out.status.images_sent);
+
+    const auto live = service.GetRugnuxStatus();
+    CHECK(live.state == RugnuxLiveState::Done);
+    REQUIRE(live.stills);
+    CHECK(live.stills->images_analysed == out.status.images_sent);
+}
+
 TEST_CASE("JFJochReceiverRugnux_Rotation", "[JFJochReceiverRugnux]") {
     // A scan stays with rugnux's own run: the start message goes out at once, and there are no stills results.
     Logger logger(Catch::getResultCapture().getCurrentTestName());