diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 5d0860b..8b8e1df 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -26,6 +26,7 @@ test:
     - cargo check --release
     - cargo fmt -- --check
     - cargo clippy -- -D warnings
+    - cargo test
   only:
     - branches
     - merge_requests
diff --git a/src/health.rs b/src/health.rs
index 5eedb00..47a93f8 100644
--- a/src/health.rs
+++ b/src/health.rs
@@ -61,3 +61,47 @@ pub async fn start_health_server(port: u16) -> Result<()> {
 
     Ok(())
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_health_status_serialization() {
+        let status = HealthStatus {
+            status: "healthy".to_string(),
+            version: "0.1.0".to_string(),
+            uptime_seconds: 42,
+        };
+
+        let json = serde_json::to_string(&status).unwrap();
+        assert!(json.contains(r#""status":"healthy""#));
+        assert!(json.contains(r#""version":"0.1.0""#));
+        assert!(json.contains(r#""uptime_seconds":42"#));
+    }
+
+    #[test]
+    fn test_health_status_deserialization() {
+        let json = r#"{"status":"healthy","version":"0.1.0","uptime_seconds":42}"#;
+        let status: HealthStatus = serde_json::from_str(json).unwrap();
+        assert_eq!(status.status, "healthy");
+        assert_eq!(status.version, "0.1.0");
+        assert_eq!(status.uptime_seconds, 42);
+    }
+
+    #[test]
+    fn test_health_status_clone() {
+        let status = HealthStatus {
+            status: "healthy".to_string(),
+            version: "0.1.0".to_string(),
+            uptime_seconds: 42,
+        };
+        let cloned = status.clone();
+        assert_eq!(status.status, cloned.status);
+        assert_eq!(status.version, cloned.version);
+        assert_eq!(status.uptime_seconds, cloned.uptime_seconds);
+    }
+
+    // Note: start_health_server is tested manually/via integration tests
+    // Unit testing it requires complex async server mocking which is not practical
+}
diff --git a/src/main.rs b/src/main.rs
index 843ff49..48fc68f 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -45,6 +45,20 @@ fn init_logger() {
         .ok();
 }
 
+/// Convert HTTP(S) URL to WebSocket URL
+fn convert_to_websocket_url(url: &str) -> String {
+    if url.starts_with("http://") {
+        url.replace("http://", "ws://")
+    } else if url.starts_with("https://") {
+        url.replace("https://", "wss://")
+    } else if url.starts_with("ws://") || url.starts_with("wss://") {
+        url.to_string()
+    } else {
+        // Default to wss:// for bare domains
+        format!("wss://{}", url)
+    }
+}
+
 #[derive(Parser)]
 #[command(name = "towerops-agent")]
 #[command(about = "Towerops remote SNMP polling agent", long_about = None)]
@@ -71,16 +85,7 @@ async fn main() {
     version::check_for_updates();
 
     // Convert HTTP(S) URL to WebSocket URL
-    let ws_url = if args.api_url.starts_with("http://") {
-        args.api_url.replace("http://", "ws://")
-    } else if args.api_url.starts_with("https://") {
-        args.api_url.replace("https://", "wss://")
-    } else if args.api_url.starts_with("ws://") || args.api_url.starts_with("wss://") {
-        args.api_url.clone()
-    } else {
-        // Default to wss:// for bare domains
-        format!("wss://{}", args.api_url)
-    };
+    let ws_url = convert_to_websocket_url(&args.api_url);
 
     info!("WebSocket URL: {}", ws_url);
 
@@ -133,3 +138,90 @@ async fn main() {
         }
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use log::Log;
+
+    #[test]
+    fn test_simple_logger_enabled() {
+        let logger = SimpleLogger {
+            level: LevelFilter::Info,
+        };
+
+        // Info level should be enabled
+        let info_metadata = log::MetadataBuilder::new()
+            .level(log::Level::Info)
+            .target("test")
+            .build();
+        assert!(logger.enabled(&info_metadata));
+
+        // Debug level should not be enabled
+        let debug_metadata = log::MetadataBuilder::new()
+            .level(log::Level::Debug)
+            .target("test")
+            .build();
+        assert!(!logger.enabled(&debug_metadata));
+
+        // Error level should be enabled
+        let error_metadata = log::MetadataBuilder::new()
+            .level(log::Level::Error)
+            .target("test")
+            .build();
+        assert!(logger.enabled(&error_metadata));
+    }
+
+    #[test]
+    fn test_simple_logger_flush() {
+        let logger = SimpleLogger {
+            level: LevelFilter::Info,
+        };
+        // flush() does nothing, just verify it's callable
+        logger.flush();
+    }
+
+    #[test]
+    fn test_convert_http_to_websocket() {
+        assert_eq!(
+            convert_to_websocket_url("http://localhost:4000"),
+            "ws://localhost:4000"
+        );
+    }
+
+    #[test]
+    fn test_convert_https_to_websocket() {
+        assert_eq!(
+            convert_to_websocket_url("https://app.towerops.com"),
+            "wss://app.towerops.com"
+        );
+    }
+
+    #[test]
+    fn test_websocket_url_unchanged() {
+        assert_eq!(
+            convert_to_websocket_url("ws://localhost:4000"),
+            "ws://localhost:4000"
+        );
+        assert_eq!(
+            convert_to_websocket_url("wss://app.towerops.com"),
+            "wss://app.towerops.com"
+        );
+    }
+
+    #[test]
+    fn test_bare_domain_gets_wss() {
+        assert_eq!(
+            convert_to_websocket_url("app.towerops.com"),
+            "wss://app.towerops.com"
+        );
+        assert_eq!(
+            convert_to_websocket_url("localhost:4000"),
+            "wss://localhost:4000"
+        );
+    }
+
+    // Note: main() function and init_logger() are not unit tested as they
+    // involve global state and tokio runtime initialization.
+    // They are tested via manual/integration testing.
+}
diff --git a/src/ping.rs b/src/ping.rs
index 83ce5e4..ebcae8c 100644
--- a/src/ping.rs
+++ b/src/ping.rs
@@ -108,7 +108,7 @@ fn build_icmp_echo_request(identifier: u16, sequence: u16) -> Vec<u8> {
 }
 
 fn parse_icmp_reply(packet: &[u8], expected_identifier: u16, expected_sequence: u16) -> Result<()> {
-    // ICMP reply might be wrapped in an IP header (20 bytes minimum)
+    // ICMP reply might be wrapped in an IP header
     // Try both raw ICMP and IP-wrapped formats
 
     // Try to parse as raw ICMP first
@@ -116,14 +116,40 @@ fn parse_icmp_reply(packet: &[u8], expected_identifier: u16, expected_sequence:
         return Ok(());
     }
 
-    // Try to parse with IP header (skip first 20 bytes)
-    if packet.len() > 20 {
-        if let Ok(()) = try_parse_icmp(&packet[20..], expected_identifier, expected_sequence) {
-            return Ok(());
+    // Check if this looks like an IP packet (version 4 in high nibble of first byte)
+    if packet.len() >= 20 && (packet[0] >> 4) == 4 {
+        // Extract IP header length from IHL field (low nibble of first byte)
+        // IHL is in 32-bit words, so multiply by 4 to get bytes
+        let ihl = (packet[0] & 0x0F) as usize * 4;
+
+        if ihl >= 20 && packet.len() > ihl {
+            // Try to parse ICMP after skipping the IP header
+            if let Ok(()) = try_parse_icmp(&packet[ihl..], expected_identifier, expected_sequence) {
+                return Ok(());
+            }
         }
     }
 
-    Err(anyhow!("Invalid ICMP reply packet"))
+    // Log diagnostic information to help debug
+    let packet_preview = if packet.len() >= 8 {
+        format!(
+            "type={} code={} id={} seq={} len={}",
+            packet[0],
+            packet.get(1).unwrap_or(&0),
+            u16::from_be_bytes([*packet.get(4).unwrap_or(&0), *packet.get(5).unwrap_or(&0)]),
+            u16::from_be_bytes([*packet.get(6).unwrap_or(&0), *packet.get(7).unwrap_or(&0)]),
+            packet.len()
+        )
+    } else {
+        format!("len={} (too short)", packet.len())
+    };
+
+    Err(anyhow!(
+        "Invalid ICMP reply packet (expected id={}, seq={}): {}",
+        expected_identifier,
+        expected_sequence,
+        packet_preview
+    ))
 }
 
 fn try_parse_icmp(packet: &[u8], expected_identifier: u16, expected_sequence: u16) -> Result<()> {
@@ -183,18 +209,24 @@ mod tests {
 
     #[test]
     fn test_icmp_checksum() {
-        // Known ICMP echo request packet with correct checksum
-        let packet = vec![
-            0x08, 0x00, 0xf7, 0xff, 0x00, 0x01, 0x00, 0x01, 0x61, 0x62, 0x63, 0x64,
+        // Test that checksum calculation is consistent
+        // ICMP echo request packet: type=8, code=0, id=1, seq=1, data="abcd"
+        let mut packet = vec![
+            0x08, 0x00, 0x00, 0x00, 0x00, 0x01, 0x00, 0x01, 0x61, 0x62, 0x63, 0x64,
         ];
 
-        // Calculate checksum for packet with checksum field zeroed
-        let mut test_packet = packet.clone();
-        test_packet[2] = 0;
-        test_packet[3] = 0;
+        // Calculate checksum
+        let checksum = icmp_checksum(&packet);
+        assert_ne!(checksum, 0, "Checksum should not be zero");
 
-        let checksum = icmp_checksum(&test_packet);
-        assert_eq!(checksum, 0xf7ff);
+        // Insert checksum into packet
+        packet[2..4].copy_from_slice(&checksum.to_be_bytes());
+
+        // Verify: recalculating checksum with checksum field included should give 0
+        // (because the sum of all words including the checksum should wrap to 0xFFFF,
+        // and one's complement of 0xFFFF is 0)
+        let verification = icmp_checksum(&packet);
+        assert_eq!(verification, 0, "Checksum verification should be 0");
     }
 
     #[test]
@@ -217,4 +249,102 @@ mod tests {
         let checksum = u16::from_be_bytes([packet[2], packet[3]]);
         assert_ne!(checksum, 0);
     }
+
+    #[test]
+    fn test_try_parse_icmp_success() {
+        // Valid ICMP echo reply packet
+        let packet = vec![
+            0x00, 0x00, 0x00, 0x00, // type=0 (reply), code=0, checksum
+            0x12, 0x34, // identifier
+            0x56, 0x78, // sequence
+            0x61, 0x62, 0x63, 0x64, // data
+        ];
+
+        let result = try_parse_icmp(&packet, 0x1234, 0x5678);
+        assert!(result.is_ok());
+    }
+
+    #[test]
+    fn test_try_parse_icmp_too_short() {
+        let packet = vec![0x00, 0x00, 0x00];
+        let result = try_parse_icmp(&packet, 0x1234, 0x5678);
+        assert!(result.is_err());
+        assert!(result.unwrap_err().to_string().contains("too short"));
+    }
+
+    #[test]
+    fn test_try_parse_icmp_wrong_type() {
+        let packet = vec![
+            0x08, 0x00, 0x00, 0x00, // type=8 (request, not reply), code=0
+            0x12, 0x34, // identifier
+            0x56, 0x78, // sequence
+        ];
+
+        let result = try_parse_icmp(&packet, 0x1234, 0x5678);
+        assert!(result.is_err());
+        assert!(result.unwrap_err().to_string().contains("mismatch"));
+    }
+
+    #[test]
+    fn test_try_parse_icmp_wrong_identifier() {
+        let packet = vec![
+            0x00, 0x00, 0x00, 0x00, // type=0, code=0
+            0x99, 0x99, // wrong identifier
+            0x56, 0x78, // sequence
+        ];
+
+        let result = try_parse_icmp(&packet, 0x1234, 0x5678);
+        assert!(result.is_err());
+    }
+
+    #[test]
+    fn test_parse_icmp_reply_raw() {
+        // Raw ICMP packet (no IP header)
+        let packet = vec![
+            0x00, 0x00, 0x00, 0x00, // type=0, code=0, checksum
+            0x12, 0x34, // identifier
+            0x56, 0x78, // sequence
+        ];
+
+        let result = parse_icmp_reply(&packet, 0x1234, 0x5678);
+        assert!(result.is_ok());
+    }
+
+    #[test]
+    fn test_parse_icmp_reply_with_ip_header() {
+        // IPv4 packet with ICMP payload
+        let packet = vec![
+            0x45, 0x00, 0x00, 0x54, // IPv4 header: version=4, IHL=5 (20 bytes)
+            0x00, 0x00, 0x00, 0x00, 0x40, 0x01, 0x00, 0x00, // TTL, protocol=ICMP
+            0xc0, 0xa8, 0x01, 0x01, // Source IP
+            0xc0, 0xa8, 0x01, 0x02, // Dest IP
+            // ICMP payload starts here (at byte 20)
+            0x00, 0x00, 0x00, 0x00, // type=0, code=0, checksum
+            0x12, 0x34, // identifier
+            0x56, 0x78, // sequence
+        ];
+
+        let result = parse_icmp_reply(&packet, 0x1234, 0x5678);
+        assert!(result.is_ok());
+    }
+
+    #[test]
+    fn test_parse_icmp_reply_invalid() {
+        let packet = vec![0x00, 0x00];
+        let result = parse_icmp_reply(&packet, 0x1234, 0x5678);
+        assert!(result.is_err());
+        assert!(result
+            .unwrap_err()
+            .to_string()
+            .contains("Invalid ICMP reply"));
+    }
+
+    #[test]
+    fn test_parse_icmp_reply_short_packet_error_message() {
+        let packet = vec![0x01, 0x02, 0x03];
+        let result = parse_icmp_reply(&packet, 0x1234, 0x5678);
+        assert!(result.is_err());
+        let err_msg = result.unwrap_err().to_string();
+        assert!(err_msg.contains("too short"));
+    }
 }
diff --git a/src/snmp/client.rs b/src/snmp/client.rs
index 170e4fb..368943d 100644
--- a/src/snmp/client.rs
+++ b/src/snmp/client.rs
@@ -216,3 +216,205 @@ fn map_snmp_error(err: snmp::SnmpError) -> SnmpError {
         _ => SnmpError::RequestFailed(format!("{:?}", err)),
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_snmp_client_new() {
+        let client = SnmpClient::new();
+        // Just verify we can create it
+        assert!(format!("{:?}", client).contains("SnmpClient"));
+    }
+
+    #[test]
+    fn test_snmp_client_default() {
+        let client = SnmpClient::default();
+        assert!(format!("{:?}", client).contains("SnmpClient"));
+    }
+
+    #[test]
+    fn test_parse_oid_valid() {
+        let result = parse_oid("1.3.6.1.2.1.1.1.0");
+        assert!(result.is_ok());
+        assert_eq!(result.unwrap(), vec![1, 3, 6, 1, 2, 1, 1, 1, 0]);
+    }
+
+    #[test]
+    fn test_parse_oid_single() {
+        let result = parse_oid("1");
+        assert!(result.is_ok());
+        assert_eq!(result.unwrap(), vec![1]);
+    }
+
+    #[test]
+    fn test_parse_oid_invalid() {
+        let result = parse_oid("1.3.6.abc.2.1");
+        assert!(result.is_err());
+        match result {
+            Err(SnmpError::InvalidOid(msg)) => {
+                assert!(msg.contains("abc"));
+            }
+            _ => panic!("Expected InvalidOid error"),
+        }
+    }
+
+    #[test]
+    fn test_parse_oid_empty() {
+        let result = parse_oid("");
+        assert!(result.is_err());
+    }
+
+    #[test]
+    fn test_format_oid() {
+        let oid = vec![1, 3, 6, 1, 2, 1, 1, 1, 0];
+        let result = format_oid(&oid);
+        assert_eq!(result, "1.3.6.1.2.1.1.1.0");
+    }
+
+    #[test]
+    fn test_format_oid_single() {
+        let oid = vec![42];
+        let result = format_oid(&oid);
+        assert_eq!(result, "42");
+    }
+
+    #[test]
+    fn test_format_oid_empty() {
+        let oid = vec![];
+        let result = format_oid(&oid);
+        assert_eq!(result, "");
+    }
+
+    #[test]
+    fn test_starts_with_true() {
+        let oid = vec![1, 3, 6, 1, 2, 1, 1, 1, 0];
+        let base = vec![1, 3, 6, 1];
+        assert!(starts_with(&oid, &base));
+    }
+
+    #[test]
+    fn test_starts_with_exact_match() {
+        let oid = vec![1, 3, 6, 1];
+        let base = vec![1, 3, 6, 1];
+        assert!(starts_with(&oid, &base));
+    }
+
+    #[test]
+    fn test_starts_with_false() {
+        let oid = vec![1, 3, 6, 1, 2, 1];
+        let base = vec![1, 3, 7];
+        assert!(!starts_with(&oid, &base));
+    }
+
+    #[test]
+    fn test_starts_with_oid_too_short() {
+        let oid = vec![1, 3];
+        let base = vec![1, 3, 6, 1];
+        assert!(!starts_with(&oid, &base));
+    }
+
+    #[test]
+    fn test_convert_value_integer() {
+        let value = snmp::Value::Integer(42);
+        let result = convert_value(value).unwrap();
+        match result {
+            SnmpValue::Integer(v) => assert_eq!(v, 42),
+            _ => panic!("Expected Integer"),
+        }
+    }
+
+    #[test]
+    fn test_convert_value_octet_string() {
+        let value = snmp::Value::OctetString(b"test".as_slice());
+        let result = convert_value(value).unwrap();
+        match result {
+            SnmpValue::String(s) => assert_eq!(s, "test"),
+            _ => panic!("Expected String"),
+        }
+    }
+
+    #[test]
+    fn test_convert_value_counter32() {
+        let value = snmp::Value::Counter32(12345);
+        let result = convert_value(value).unwrap();
+        match result {
+            SnmpValue::Counter32(v) => assert_eq!(v, 12345),
+            _ => panic!("Expected Counter32"),
+        }
+    }
+
+    #[test]
+    fn test_convert_value_counter64() {
+        let value = snmp::Value::Counter64(9876543210);
+        let result = convert_value(value).unwrap();
+        match result {
+            SnmpValue::Counter64(v) => assert_eq!(v, 9876543210),
+            _ => panic!("Expected Counter64"),
+        }
+    }
+
+    #[test]
+    fn test_convert_value_unsigned32() {
+        let value = snmp::Value::Unsigned32(999);
+        let result = convert_value(value).unwrap();
+        match result {
+            SnmpValue::Gauge32(v) => assert_eq!(v, 999),
+            _ => panic!("Expected Gauge32"),
+        }
+    }
+
+    #[test]
+    fn test_convert_value_timeticks() {
+        let value = snmp::Value::Timeticks(12345678);
+        let result = convert_value(value).unwrap();
+        match result {
+            SnmpValue::TimeTicks(v) => assert_eq!(v, 12345678),
+            _ => panic!("Expected TimeTicks"),
+        }
+    }
+
+    #[test]
+    fn test_convert_value_ip_address() {
+        let value = snmp::Value::IpAddress([192, 168, 1, 1]);
+        let result = convert_value(value).unwrap();
+        match result {
+            SnmpValue::IpAddress(ip) => assert_eq!(ip, "192.168.1.1"),
+            _ => panic!("Expected IpAddress"),
+        }
+    }
+
+    #[test]
+    fn test_map_snmp_error_send() {
+        let err = snmp::SnmpError::SendError;
+        let result = map_snmp_error(err);
+        match result {
+            SnmpError::NetworkUnreachable => {}
+            _ => panic!("Expected NetworkUnreachable"),
+        }
+    }
+
+    #[test]
+    fn test_map_snmp_error_receive() {
+        let err = snmp::SnmpError::ReceiveError;
+        let result = map_snmp_error(err);
+        match result {
+            SnmpError::Timeout => {}
+            _ => panic!("Expected Timeout"),
+        }
+    }
+
+    #[test]
+    fn test_map_snmp_error_community() {
+        let err = snmp::SnmpError::CommunityMismatch;
+        let result = map_snmp_error(err);
+        match result {
+            SnmpError::AuthFailure => {}
+            _ => panic!("Expected AuthFailure"),
+        }
+    }
+
+    // Note: get() and walk() methods require actual network operations
+    // and are tested via integration tests, not unit tests
+}
diff --git a/src/snmp/types.rs b/src/snmp/types.rs
index c8552b6..205d3fd 100644
--- a/src/snmp/types.rs
+++ b/src/snmp/types.rs
@@ -54,3 +54,57 @@ impl SnmpValue {
         self.as_i64().map(|v| v as f64)
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_snmp_error_display() {
+        assert_eq!(
+            format!("{}", SnmpError::RequestFailed("test error".to_string())),
+            "SNMP request failed: test error"
+        );
+        assert_eq!(
+            format!("{}", SnmpError::InvalidOid("1.2.3".to_string())),
+            "Invalid OID: 1.2.3"
+        );
+        assert_eq!(format!("{}", SnmpError::Timeout), "Timeout");
+        assert_eq!(
+            format!("{}", SnmpError::AuthFailure),
+            "Authentication failure"
+        );
+        assert_eq!(
+            format!("{}", SnmpError::NetworkUnreachable),
+            "Network unreachable"
+        );
+    }
+
+    #[test]
+    fn test_snmp_error_is_error() {
+        let error: &dyn std::error::Error = &SnmpError::Timeout;
+        assert_eq!(format!("{}", error), "Timeout");
+    }
+
+    #[test]
+    fn test_snmp_value_as_i64() {
+        assert_eq!(SnmpValue::Integer(42).as_i64(), Some(42));
+        assert_eq!(SnmpValue::Counter32(100).as_i64(), Some(100));
+        assert_eq!(SnmpValue::Counter64(1000).as_i64(), Some(1000));
+        assert_eq!(SnmpValue::Gauge32(50).as_i64(), Some(50));
+        assert_eq!(SnmpValue::TimeTicks(200).as_i64(), Some(200));
+        assert_eq!(SnmpValue::String("test".to_string()).as_i64(), None);
+        assert_eq!(SnmpValue::IpAddress("1.2.3.4".to_string()).as_i64(), None);
+    }
+
+    #[test]
+    fn test_snmp_value_as_f64() {
+        assert_eq!(SnmpValue::Integer(42).as_f64(), Some(42.0));
+        assert_eq!(SnmpValue::Counter32(100).as_f64(), Some(100.0));
+        assert_eq!(SnmpValue::Counter64(1000).as_f64(), Some(1000.0));
+        assert_eq!(SnmpValue::Gauge32(50).as_f64(), Some(50.0));
+        assert_eq!(SnmpValue::TimeTicks(200).as_f64(), Some(200.0));
+        assert_eq!(SnmpValue::String("test".to_string()).as_f64(), None);
+        assert_eq!(SnmpValue::IpAddress("1.2.3.4".to_string()).as_f64(), None);
+    }
+}
diff --git a/src/version.rs b/src/version.rs
index b393f2f..de76336 100644
--- a/src/version.rs
+++ b/src/version.rs
@@ -107,6 +107,13 @@ fn get_latest_version() -> Result<String, Box<dyn std::error::Error>> {
         .call()?
         .into_json()?;
 
+    extract_latest_version_from_response(response)
+}
+
+/// Extract the latest version from Docker Hub response
+fn extract_latest_version_from_response(
+    response: DockerHubResponse,
+) -> Result<String, Box<dyn std::error::Error>> {
     // Filter for semver tags and find the latest
     let mut versions: Vec<Version> = response
         .results
@@ -122,3 +129,163 @@ fn get_latest_version() -> Result<String, Box<dyn std::error::Error>> {
         .map(|v| format!("{}.{}.{}", v.major, v.minor, v.patch))
         .ok_or_else(|| "No valid semver tags found".into())
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_current_version() {
+        let version = current_version();
+        assert!(!version.is_empty(), "Version should not be empty");
+        // Version comes from env! macro at compile time
+        // Just verify it's a non-empty string
+    }
+
+    #[test]
+    fn test_version_parse_valid() {
+        let v = Version::parse("1.2.3").unwrap();
+        assert_eq!(v.major, 1);
+        assert_eq!(v.minor, 2);
+        assert_eq!(v.patch, 3);
+    }
+
+    #[test]
+    fn test_version_parse_with_v_prefix() {
+        let v = Version::parse("v2.5.8").unwrap();
+        assert_eq!(v.major, 2);
+        assert_eq!(v.minor, 5);
+        assert_eq!(v.patch, 8);
+    }
+
+    #[test]
+    fn test_version_parse_invalid() {
+        assert!(Version::parse("1.2").is_none());
+        assert!(Version::parse("1.2.3.4").is_none());
+        assert!(Version::parse("a.b.c").is_none());
+        assert!(Version::parse("1.2.x").is_none());
+        assert!(Version::parse("").is_none());
+    }
+
+    #[test]
+    fn test_version_comparison_major() {
+        let v1 = Version::parse("2.0.0").unwrap();
+        let v2 = Version::parse("1.9.9").unwrap();
+        assert!(v1 > v2);
+        assert!(v2 < v1);
+    }
+
+    #[test]
+    fn test_version_comparison_minor() {
+        let v1 = Version::parse("1.5.0").unwrap();
+        let v2 = Version::parse("1.4.9").unwrap();
+        assert!(v1 > v2);
+        assert!(v2 < v1);
+    }
+
+    #[test]
+    fn test_version_comparison_patch() {
+        let v1 = Version::parse("1.2.4").unwrap();
+        let v2 = Version::parse("1.2.3").unwrap();
+        assert!(v1 > v2);
+        assert!(v2 < v1);
+    }
+
+    #[test]
+    fn test_version_comparison_equal() {
+        let v1 = Version::parse("1.2.3").unwrap();
+        let v2 = Version::parse("1.2.3").unwrap();
+        assert_eq!(v1, v2);
+        assert!(!(v1 > v2));
+        assert!(!(v1 < v2));
+    }
+
+    #[test]
+    fn test_version_sorting() {
+        let mut versions = vec![
+            Version::parse("1.2.3").unwrap(),
+            Version::parse("2.0.0").unwrap(),
+            Version::parse("1.5.0").unwrap(),
+            Version::parse("1.2.10").unwrap(),
+        ];
+        versions.sort();
+        assert_eq!(versions[0], Version::parse("1.2.3").unwrap());
+        assert_eq!(versions[1], Version::parse("1.2.10").unwrap());
+        assert_eq!(versions[2], Version::parse("1.5.0").unwrap());
+        assert_eq!(versions[3], Version::parse("2.0.0").unwrap());
+    }
+
+    #[test]
+    fn test_dockerhub_response_deserialize() {
+        let json = r#"{"results":[{"name":"v1.0.0"},{"name":"v1.0.1"}]}"#;
+        let response: DockerHubResponse = serde_json::from_str(json).unwrap();
+        assert_eq!(response.results.len(), 2);
+        assert_eq!(response.results[0].name, "v1.0.0");
+        assert_eq!(response.results[1].name, "v1.0.1");
+    }
+
+    #[test]
+    fn test_extract_latest_version_from_response() {
+        let response = DockerHubResponse {
+            results: vec![
+                DockerHubTag {
+                    name: "v1.0.0".to_string(),
+                },
+                DockerHubTag {
+                    name: "v1.2.0".to_string(),
+                },
+                DockerHubTag {
+                    name: "v1.1.5".to_string(),
+                },
+                DockerHubTag {
+                    name: "latest".to_string(),
+                }, // Should be ignored
+            ],
+        };
+
+        let latest = extract_latest_version_from_response(response).unwrap();
+        assert_eq!(latest, "1.2.0");
+    }
+
+    #[test]
+    fn test_extract_latest_version_no_valid_tags() {
+        let response = DockerHubResponse {
+            results: vec![
+                DockerHubTag {
+                    name: "latest".to_string(),
+                },
+                DockerHubTag {
+                    name: "main".to_string(),
+                },
+            ],
+        };
+
+        let result = extract_latest_version_from_response(response);
+        assert!(result.is_err());
+        assert!(result.unwrap_err().to_string().contains("No valid semver"));
+    }
+
+    #[test]
+    fn test_extract_latest_version_empty() {
+        let response = DockerHubResponse { results: vec![] };
+
+        let result = extract_latest_version_from_response(response);
+        assert!(result.is_err());
+    }
+
+    #[test]
+    fn test_version_debug() {
+        let v = Version {
+            major: 1,
+            minor: 2,
+            patch: 3,
+        };
+        let debug_str = format!("{:?}", v);
+        assert!(debug_str.contains("1"));
+        assert!(debug_str.contains("2"));
+        assert!(debug_str.contains("3"));
+    }
+
+    // Note: check_for_updates() and get_latest_version() are tested via integration tests
+    // as they require network access to Docker Hub
+}
diff --git a/src/websocket_client.rs b/src/websocket_client.rs
index 9429eb1..ee51b74 100644
--- a/src/websocket_client.rs
+++ b/src/websocket_client.rs
@@ -511,3 +511,112 @@ async fn run_monitoring_task(
 
     Ok(())
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_value_to_string_integer() {
+        let value = SnmpValue::Integer(42);
+        assert_eq!(value_to_string(value), "42");
+    }
+
+    #[test]
+    fn test_value_to_string_string() {
+        let value = SnmpValue::String("test".to_string());
+        assert_eq!(value_to_string(value), "test");
+    }
+
+    #[test]
+    fn test_value_to_string_counter32() {
+        let value = SnmpValue::Counter32(12345);
+        assert_eq!(value_to_string(value), "12345");
+    }
+
+    #[test]
+    fn test_value_to_string_counter64() {
+        let value = SnmpValue::Counter64(9876543210);
+        assert_eq!(value_to_string(value), "9876543210");
+    }
+
+    #[test]
+    fn test_value_to_string_gauge32() {
+        let value = SnmpValue::Gauge32(999);
+        assert_eq!(value_to_string(value), "999");
+    }
+
+    #[test]
+    fn test_value_to_string_timeticks() {
+        let value = SnmpValue::TimeTicks(12345678);
+        assert_eq!(value_to_string(value), "12345678");
+    }
+
+    #[test]
+    fn test_value_to_string_ip_address() {
+        let value = SnmpValue::IpAddress("192.168.1.1".to_string());
+        assert_eq!(value_to_string(value), "192.168.1.1");
+    }
+
+    #[test]
+    fn test_generate_agent_id() {
+        let id = generate_agent_id();
+        assert!(id.starts_with("agent-"));
+
+        // Verify the timestamp part is a number
+        let timestamp_str = id.strip_prefix("agent-").unwrap();
+        let timestamp: u64 = timestamp_str.parse().expect("Timestamp should be a number");
+        assert!(timestamp > 0);
+    }
+
+    #[test]
+    fn test_get_uptime_seconds() {
+        let uptime = get_uptime_seconds();
+        // Currently returns 0 (not implemented), just verify it's callable
+        assert_eq!(uptime, 0);
+    }
+
+    #[test]
+    fn test_get_local_ip() {
+        let ip = get_local_ip();
+        // Currently returns None (not implemented), just verify it's callable
+        assert!(ip.is_none());
+    }
+
+    #[test]
+    fn test_phoenix_message_serialization() {
+        let msg = PhoenixMessage {
+            topic: "agent:123".to_string(),
+            event: "phx_join".to_string(),
+            payload: serde_json::json!({"token": "test"}),
+            reference: Some("1".to_string()),
+        };
+
+        let json = serde_json::to_string(&msg).unwrap();
+        assert!(json.contains("agent:123"));
+        assert!(json.contains("phx_join"));
+        assert!(json.contains("token"));
+        assert!(json.contains("test"));
+    }
+
+    #[test]
+    fn test_phoenix_message_deserialization() {
+        let json =
+            r#"{"topic":"agent:123","event":"phx_reply","payload":{"status":"ok"},"ref":"1"}"#;
+        let msg: PhoenixMessage = serde_json::from_str(json).unwrap();
+        assert_eq!(msg.topic, "agent:123");
+        assert_eq!(msg.event, "phx_reply");
+        assert_eq!(msg.reference, Some("1".to_string()));
+    }
+
+    #[test]
+    fn test_phoenix_message_no_reference() {
+        let json = r#"{"topic":"agent:123","event":"job","payload":{},"ref":null}"#;
+        let msg: PhoenixMessage = serde_json::from_str(json).unwrap();
+        assert_eq!(msg.topic, "agent:123");
+        assert_eq!(msg.event, "job");
+        assert!(msg.reference.is_none());
+    }
+
+    // Note: AgentClient methods require WebSocket connection and are tested via integration tests
+}