diff --git a/tests/trace.rs b/tests/trace.rs
new file mode 100644
index 0000000..34384f7
--- /dev/null
+++ b/tests/trace.rs
@@ -0,0 +1,203 @@
+use nom::FindSubstring;
+use smtp_codec::{
+    parse::{
+        command::command,
+        response::{ehlo_ok_rsp, Greeting, Reply_line},
+    },
+    types::Command,
+};
+
+fn parse_trace(mut trace: &[u8]) {
+    let (rem, greeting) = Greeting(trace).unwrap();
+    println!("S: {:?}", greeting);
+    trace = rem;
+
+    loop {
+        if trace.is_empty() {
+            break;
+        }
+
+        let (rem, cmd) = command(trace).unwrap();
+        println!("C: {:?}", cmd);
+        trace = rem;
+
+        match cmd {
+            Command::Ehlo { .. } => {
+                let (rem, rsp) = ehlo_ok_rsp(trace).unwrap();
+                println!("S: {:?}", rsp);
+                trace = rem;
+            }
+            Command::Data { .. } => {
+                let (rem, rsp) = Reply_line(trace).unwrap();
+                println!("S: {:?}", rsp);
+                trace = rem;
+
+                let pos = trace.find_substring("\r\n.\r\n").unwrap();
+                let (data, rem) = trace.split_at(pos + 5);
+                println!("C (data): <{}>", std::str::from_utf8(data).unwrap());
+                trace = rem;
+
+                let (rem, rsp) = Reply_line(trace).unwrap();
+                println!("S: {:?}", rsp);
+                trace = rem;
+            }
+            _ => {
+                let (rem, rsp) = Reply_line(trace).unwrap();
+                println!("S: {:?}", rsp);
+                trace = rem;
+            }
+        }
+    }
+}
+
+#[test]
+/// D.1.  A Typical SMTP Transaction Scenario
+fn test_trace_d_1() {
+    let trace = b"\
+220 foo.com Simple Mail Transfer Service Ready\r
+EHLO bar.com\r
+250-foo.com greets bar.com\r
+250-8BITMIME\r
+250-SIZE\r
+250-DSN\r
+250 HELP\r
+MAIL FROM:<Smith@bar.com>\r
+250 OK\r
+RCPT TO:<Jones@foo.com>\r
+250 OK\r
+RCPT TO:<Green@foo.com>\r
+550 No such user here\r
+RCPT TO:<Brown@foo.com>\r
+250 OK\r
+DATA\r
+354 Start mail input; end with <CRLF>.<CRLF>\r
+Blah blah blah...\r
+...etc. etc. etc.\r
+.\r
+250 OK\r
+QUIT\r
+221 foo.com Service closing transmission channel\r
+";
+
+    parse_trace(trace);
+}
+
+#[test]
+/// D.2.  Aborted SMTP Transaction Scenario
+fn test_trace_d_2() {
+    let trace = b"\
+220 foo.com Simple Mail Transfer Service Ready\r
+EHLO bar.com\r
+250-foo.com greets bar.com\r
+250-8BITMIME\r
+250-SIZE\r
+250-DSN\r
+250 HELP\r
+MAIL FROM:<Smith@bar.com>\r
+250 OK\r
+RCPT TO:<Jones@foo.com>\r
+250 OK\r
+RCPT TO:<Green@foo.com>\r
+550 No such user here\r
+RSET\r
+250 OK\r
+QUIT\r
+221 foo.com Service closing transmission channel\r
+";
+
+    parse_trace(trace);
+}
+
+#[test]
+/// D.3.  Relayed Mail Scenario
+fn test_trace_d_3() {
+    let step_1 = b"\
+220 foo.com Simple Mail Transfer Service Ready\r
+EHLO bar.com\r
+250-foo.com greets bar.com\r
+250-8BITMIME\r
+250-SIZE\r
+250-DSN\r
+250 HELP\r
+MAIL FROM:<JQP@bar.com>\r
+250 OK\r
+RCPT TO:<Jones@XYZ.COM>\r
+250 OK\r
+DATA\r
+354 Start mail input; end with <CRLF>.<CRLF>\r
+Date: Thu, 21 May 1998 05:33:29 -0700\r
+From: John Q. Public <JQP@bar.com>\r
+Subject: The Next Meeting of the Board\r
+To: Jones@xyz.com\r
+\r
+Bill:\r
+The next meeting of the board of directors will be\r
+on Tuesday.\r
+John.\r
+.\r
+250 OK\r
+QUIT\r
+221 foo.com Service closing transmission channel\r
+";
+
+    let step_2 = b"\
+220 xyz.com Simple Mail Transfer Service Ready\r
+EHLO foo.com\r
+250 xyz.com is on the air\r
+MAIL FROM:<JQP@bar.com>\r
+250 OK\r
+RCPT TO:<Jones@XYZ.COM>\r
+250 OK\r
+DATA\r
+354 Start mail input; end with <CRLF>.<CRLF>\r
+Received: from bar.com by foo.com ; Thu, 21 May 1998\r
+    05:33:29 -0700\r
+Date: Thu, 21 May 1998 05:33:22 -0700\r
+From: John Q. Public <JQP@bar.com>\r
+Subject:  The Next Meeting of the Board\r
+To: Jones@xyz.com\r
+\r
+Bill:\r
+The next meeting of the board of directors will be\r
+on Tuesday.\r
+                        John.\r
+.\r
+250 OK\r
+QUIT\r
+221 foo.com Service closing transmission channel\r
+";
+
+    parse_trace(step_1);
+    parse_trace(step_2);
+}
+
+#[test]
+/// D.4.  Verifying and Sending Scenario
+fn test_trace_d_4() {
+    let trace = b"\
+220 foo.com Simple Mail Transfer Service Ready\r
+EHLO bar.com\r
+250-foo.com greets bar.com\r
+250-8BITMIME\r
+250-SIZE\r
+250-DSN\r
+250-VRFY\r
+250 HELP\r
+VRFY Crispin\r
+250 Mark Crispin <Admin.MRC@foo.com>\r
+MAIL FROM:<EAK@bar.com>\r
+250 OK\r
+RCPT TO:<Admin.MRC@foo.com>\r
+250 OK\r
+DATA\r
+354 Start mail input; end with <CRLF>.<CRLF>\r
+Blah blah blah...\r
+...etc. etc. etc.\r
+.\r
+250 OK\r
+QUIT\r
+221 foo.com Service closing transmission channel\r
+";
+
+    parse_trace(trace);
+}