1 files changed, 66 insertions, 0 deletions
diff --git a/logs_test.go b/logs_test.go
new file mode 100644
index 0000000..abef7eb
--- /dev/null
+++ b/logs_test.go
@@ -0,0 +1,66 @@
+package main
+
+import (
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"sync"
+	"testing"
+)
+
+// A gap in the log reads as nothing having happened, so a line that never
+// reaches the worker has to be counted and reported by one that does. The two
+// ways it fails are a send that errors and a send that is answered with an
+// error, and only the first of them looks like a failure to the client.
+func TestShipperReportsWhatDidNotLand(t *testing.T) {
+	var mu sync.Mutex
+	mode := "refuse"
+	var landed []string
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		mu.Lock()
+		defer mu.Unlock()
+		switch mode {
+		case "refuse":
+			http.Error(w, "no", http.StatusInternalServerError)
+		case "drop":
+			// A send that errors rather than answering.
+			if conn, _, err := w.(http.Hijacker).Hijack(); err == nil {
+				conn.Close()
+			}
+		default:
+			body, _ := io.ReadAll(r.Body)
+			landed = append(landed, string(body))
+			w.WriteHeader(http.StatusNoContent)
+		}
+	}))
+	defer srv.Close()
+
+	s := newShipper(srv.URL)
+	// close sends what is queued and waits, so each of these is one send.
+	for _, step := range []struct{ mode, line string }{
+		{"refuse", "answered with a 500"},
+		{"drop", "the connection went away"},
+		{"take", "this one lands"},
+	} {
+		mu.Lock()
+		mode = step.mode
+		mu.Unlock()
+		if _, err := s.Write([]byte(step.line + "\n")); err != nil {
+			t.Fatal(err)
+		}
+		s.close()
+	}
+
+	mu.Lock()
+	defer mu.Unlock()
+	if len(landed) != 1 {
+		t.Fatalf("the worker was handed %d bodies, want the one it accepted: %q", len(landed), landed)
+	}
+	if !strings.Contains(landed[0], "this one lands") {
+		t.Errorf("the line that should have landed is missing from %q", landed[0])
+	}
+	if !strings.Contains(landed[0], "2 log lines did not reach the worker") {
+		t.Errorf("the two lines that did not land are not reported in %q", landed[0])
+	}
+}