add InsinMessageFormatter

Inspectron.Epson.Tests/Telemetry/InsinMessageFormatterTests.cs

@@ -0,0 +1,52 @@
+using Inspectron.Epson.PrintServer.Telemetry;
+
+namespace Inspectron.Epson.Tests.Telemetry;
+
+public class InsinMessageFormatterTests
+{
+    [Fact]
+    public void Format_single_pair_no_spaces()
+    {
+        var result = InsinMessageFormatter.Format(("printer", "192.168.1.10"));
+        Assert.Equal("printer=192.168.1.10", result);
+    }
+
+    [Fact]
+    public void Format_multiple_pairs_joined_by_space()
+    {
+        var result = InsinMessageFormatter.Format(
+            ("printer", "192.168.1.10"),
+            ("jobId", "42"));
+        Assert.Equal("printer=192.168.1.10 jobId=42", result);
+    }
+
+    [Fact]
+    public void Format_quotes_value_containing_space()
+    {
+        var result = InsinMessageFormatter.Format(("error", "paper end detected"));
+        Assert.Equal("error=\"paper end detected\"", result);
+    }
+
+    [Fact]
+    public void Format_escapes_embedded_double_quote()
+    {
+        var result = InsinMessageFormatter.Format(("error", "he said \"nope\""));
+        Assert.Equal("error=\"he said \\\"nope\\\"\"", result);
+    }
+
+    [Fact]
+    public void Format_treats_null_or_empty_value_as_empty_string()
+    {
+        var result = InsinMessageFormatter.Format(("model", (string?)null), ("name", ""));
+        Assert.Equal("model= name=", result);
+    }
+
+    [Fact]
+    public void Format_omits_pairs_with_null_or_empty_key()
+    {
+        var result = InsinMessageFormatter.Format(
+            ("", "ignored"),
+            ("printer", "192.168.1.10"));
+        Assert.Equal("printer=192.168.1.10", result);
+    }
+}