diff --git a/src/lib.rs b/src/lib.rs
index c917aa4..15b4ef4 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -75,9 +75,232 @@ impl PSOPacketData for String {
 
 
 pub trait PSOPacket: std::fmt::Debug {
+    // const CMD: u16;
     fn from_bytes(data: &[u8]) -> Result<Self, PacketParseError> where Self: Sized;
     fn as_bytes(&self) -> Vec<u8>;
 }
 
 
 
+#[cfg(test)]
+mod test {
+    use super::*;
+    use psopacket::pso_packet2;
+
+    #[test]
+    fn test_basic_pso_packet() {
+        #[pso_packet2(0x23)]
+        struct Test {
+            a: u32,
+            b: u16,
+            c: u16,
+        }
+
+        let test = Test {
+            a: 123456789,
+            b: 54321,
+            c: 9999,
+        };
+
+        let mut bytes = test.as_bytes();
+        assert!(bytes == vec![16, 0, 35, 0, 0, 0, 0, 0, 21, 205, 91, 7, 49, 212, 15, 39]);
+
+        bytes[11] = 17;
+        let test2 = Test::from_bytes(&bytes).unwrap();
+        assert!(test2 == Test {
+            a: 291228949,
+            b: 54321,
+            c: 9999,
+        });
+    }
+
+    #[test]
+    fn test_array_in_packet() {
+        #[pso_packet2(0x23)]
+        struct Test {
+            a: u32,
+            b: u16,
+            c: [u16; 3],
+        }
+
+        let test = Test {
+            a: 123456789,
+            b: 54321,
+            c: [1111, 2222, 3333],
+        };
+
+        let mut bytes = test.as_bytes();
+        assert!(bytes == [20, 0, 35, 0, 0, 0, 0, 0, 21, 205, 91, 7, 49, 212, 87, 4, 174, 8, 5, 13]);
+
+        bytes[17] = 17;
+        let test2 = Test::from_bytes(&bytes).unwrap();
+        assert!(test2 == Test {
+            a: 123456789,
+            b: 54321,
+            c: [1111, 4526, 3333],
+        });
+
+    }
+
+    #[test]
+    fn test_custom_type_in_packet() {
+        #[derive(Clone, Debug, PartialEq)]
+        struct MyType {
+            k: u8,
+            j: u32,
+        }
+
+        impl PSOPacketData for MyType {
+            fn from_bytes<R: std::io::Read>(cursor: &mut R) -> Result<MyType, PacketParseError> {
+                let mut kb = [0u8; 1];
+                cursor.read(&mut kb).map_err(|_| PacketParseError::ReadError)?;
+                let mut jb = [0u8; 4];
+                cursor.read(&mut jb).map_err(|_| PacketParseError::ReadError)?;
+                Ok(MyType {
+                    k: kb[0],
+                    j: u32::from_le_bytes(jb)
+                })
+            }
+            fn as_bytes(&self) -> Vec<u8> {
+                let jbytes = u32::to_le_bytes(self.j);
+                vec![self.k, jbytes[0], jbytes[1], jbytes[2], jbytes[3]]
+            }
+        }
+
+        #[pso_packet2(0x23)]
+        struct Test {
+            a: u32,
+            b: u16,
+            c: MyType,
+            d: u8,
+        }
+
+
+        let test = Test {
+            a: 123456789,
+            b: 54321,
+            c: MyType {
+                k: 23,
+                j: 999999,
+            },
+            d: 5,
+        };
+
+        let mut bytes = test.as_bytes();
+        assert!(bytes == [20, 0, 35, 0, 0, 0, 0, 0, 21, 205, 91, 7, 49, 212, 23, 63, 66, 15, 0, 5]);
+        bytes[17] = 17;
+        let test2 = Test::from_bytes(&bytes).unwrap();
+        assert!(test2 == Test {
+            a: 123456789,
+            b: 54321,
+            c: MyType {
+                k: 23,
+                j: 1131071,
+            },
+            d: 5,
+        });
+    }
+
+    #[test]
+    fn test_string_in_packet() {
+        #[pso_packet2(0x23)]
+        struct Test {
+            a: u32,
+            b: u16,
+            s: String,
+        }
+
+        let test = Test {
+            a: 123456789,
+            b: 54321,
+            s: "asdf あえいおう".to_string(),
+        };
+
+        let mut bytes = test.as_bytes();
+        assert!(bytes == vec![36, 0, 35, 0, 0, 0, 0, 0, 21, 205, 91, 7, 49, 212, 97, 0, 115, 0, 100, 0,
+                              102, 0, 32, 0, 66, 48, 72, 48, 68, 48, 74, 48, 70, 48, 0, 0]);
+        bytes[18] = 99;
+        let test2 = Test::from_bytes(&bytes).unwrap();
+        assert!(test2 == Test {
+            a: 123456789,
+            b: 54321,
+            s: "ascf あえいおう\u{0}".to_string(),
+        });
+    }
+
+    #[test]
+    fn test_vec_in_packet() {
+        #[pso_packet2(0x23)]
+        struct Test {
+            a: u32,
+            b: u16,
+            v: Vec<u16>,
+        }
+
+        let test = Test {
+            a: 123456789,
+            b: 54321,
+            v: vec![123,456,789],
+        };
+
+        let mut bytes = test.as_bytes();
+        assert!(bytes == vec![20, 0, 35, 0, 3, 0, 0, 0, 21, 205, 91, 7, 49, 212, 123, 0, 200, 1, 21, 3]);
+        bytes[18] = 99;
+        let test2 = Test::from_bytes(&bytes).unwrap();
+        assert!(test2 == Test {
+            a: 123456789,
+            b: 54321,
+            v: vec![123,456,867],
+        });
+    }
+
+    #[test]
+    fn test_no_flag_packet() {
+        #[pso_packet2(0x23, no_flag)]
+        struct Test {
+            a: u32,
+            b: u16,
+            c: u16,
+        }
+
+        let test = Test {
+            a: 123456789,
+            b: 54321,
+            c: 9999,
+        };
+
+        let mut bytes = test.as_bytes();
+        assert!(bytes == vec![12, 0, 35, 0, 21, 205, 91, 7, 49, 212, 15, 39]);
+
+        bytes[11] = 17;
+        let test2 = Test::from_bytes(&bytes).unwrap();
+        assert!(test2 == Test {
+            a: 123456789,
+            b: 54321,
+            c: 4367,
+        });
+    }
+
+    #[test]
+    fn test_command_error() {
+        #[pso_packet2(0x23)]
+        struct Test {
+            a: u32,
+            b: u16,
+            c: u16,
+        }
+
+        let test = Test {
+            a: 123456789,
+            b: 54321,
+            c: 9999,
+        };
+
+        let mut bytes = test.as_bytes();
+        assert!(bytes == vec![16, 0, 35, 0, 0, 0, 0, 0, 21, 205, 91, 7, 49, 212, 15, 39]);
+
+        bytes[2] = 17;
+        let test2 = Test::from_bytes(&bytes);
+        assert!(test2 == Err(PacketParseError::WrongPacketCommand));
+    }
+}