preserve newlines

lib/lamian/log_device.rb

@@ -26,7 +26,8 @@ def string # :nodoc:
     def truncate(msg)
       return msg unless msg.size > max_log_length
 
-      suffix = "..."
+      suffix = +"..."
+      suffix << "\n" if msg.end_with?("\n")
       msg = msg[0, max_log_length - suffix.size]
 
       "#{msg}#{suffix}"

spec/lamian/log_device_spec.rb

@@ -4,18 +4,27 @@
   subject(:logdev) { described_class.new(max_log_lines: 5, max_log_length: 20) }
 
   it "saves log" do
-    logdev.write("Hello ")
-    logdev.write("world!")
-    expect(logdev.string).to eq("Hello world!")
+    logdev.write("Hello\n")
+    logdev.write("world!\n")
+    expect(logdev.string).to eq("Hello\nworld!\n")
   end
 
   it "only stores 5 latest log lines" do
     8.times { |x| logdev.write(x + 1) }
     expect(logdev.string).to eq("45678")
   end
 
-  it "truncates long lines" do
-    logdev.write("Hello world, this is me!")
-    expect(logdev.string).to eq("Hello world, this...")
+  context "long log lines" do
+    it "truncates log" do
+      logdev.write("Hello world, this is me!")
+      expect(logdev.string).to eq("Hello world, this...")
+    end
+
+    context "line with newline in the end" do
+      it "truncates log and adds newline" do
+        logdev.write("Hello world, this is me!\n")
+        expect(logdev.string).to eq("Hello world, thi...\n")
+      end
+    end
   end
 end