diff --git a/doc/todo.md b/doc/todo.md
index 858243a..f6129ae 100644
--- a/doc/todo.md
+++ b/doc/todo.md
@@ -22,7 +22,7 @@
 - Write out what bus transactions look like and how messages get passed. probably going to need wavedrom for this.
 
 ## Testing
-- need to add tests for the python itself - does it recognize bad yaml files and produce the right errors when trying to build from them? are good manta files synthesizeable?
+- need to build out more tests for the python itself in test/api_gen
 - try doing literally anything on Windows lol
 
 ## Meta
diff --git a/src/manta/__init__.py b/src/manta/__init__.py
index a6419cf..813bbcc 100644
--- a/src/manta/__init__.py
+++ b/src/manta/__init__.py
@@ -54,15 +54,14 @@ class UARTInterface:
             if (port.vid == 0x403) and (port.pid == 0x6010):
                 recognized_devices.append(port)     
         
-        assert len(recognized_devices) == 2, f"Expected to see two serial ports for FT2232 device, but instead see {len(recognized_devices)}."
-
-
         # board manufacturers seem to always make the 0th serial
         # interface on the FT2232 be for programming over JTAG,
         # and then the 1st to be for UART. as a result, we always
         # grab the device with the larger location
 
         rd = recognized_devices
+        assert len(recognized_devices) == 2, f"Expected to see two serial ports for FT2232 device, but instead see {len(recognized_devices)}."
+        assert rd[0].serial_number == rd[1].serial_number, "Serial numbers should be the same on both FT2232 ports - probably somehow grabbed ports on two different devices."
         return rd[0].device if rd[0].location > rd[1].location else rd[1].device
 
     def read_register(self, addr):
@@ -936,8 +935,15 @@ Supported commands:
     elif argv[1] == "ports":
         import serial.tools.list_ports
 
-        for info in serial.tools.list_ports.comports():
-            print(info)
+        for port in serial.tools.list_ports.comports():
+            print(port)
+            print(' ->  vid: 0x{:04X}'.format(port.vid))
+            print(' ->  pid: 0x{:04X}'.format(port.pid))
+            print(f" ->  ser: {port.serial_number}")
+            print(f" ->  loc: {port.location}")
+            print(f" -> mftr: {port.manufacturer}")
+            print(f" -> prod: {port.product}")
+            print(f" -> desc: {port.description}\n")
 
     # generate the specified configuration
     elif argv[1] == "gen":
diff --git a/test/api_gen/invalid_configs/0_mangled_yaml.yaml b/test/api_gen/invalid_configs/0_mangled_yaml.yaml
new file mode 100644
index 0000000..866e678
--- /dev/null
+++ b/test/api_gen/invalid_configs/0_mangled_yaml.yaml
@@ -0,0 +1,26 @@
+---
+cores:
+  my_io_core:
+    type: io
+
+    inputs:
+      btnu: 1
+      btnd: 1
+      btnl: Q 
+      btnr: 1
+      btnc: 1
+      sw: 16
+
+    outputs:
+      led: 16
+      led16_b: 1
+      led16_g: 1
+      led16_r: 1
+      led17_b: 1
+      led17_g: 1
+      led17_r: 1
+
+uart:
+  port: "auto"
+  baudrate: 115200
+  clock_freq: 100000000
\ No newline at end of file
diff --git a/test/api_gen/invalid_configs/1_mangled_yaml.yaml b/test/api_gen/invalid_configs/1_mangled_yaml.yaml
new file mode 100644
index 0000000..c786cdb
--- /dev/null
+++ b/test/api_gen/invalid_configs/1_mangled_yaml.yaml
@@ -0,0 +1,26 @@
+---
+cores:
+  my_io_core:
+    type: io
+
+    inputs:
+      btnu: 1
+      btnd: 1
+      btnl: 1
+      btnr: 1
+      btnc: 
+      sw: 16
+
+    outputs:
+      led: 16
+      led16_b: 1
+      led16_g: 1
+      led16_r: 1
+      led17_b: 1
+      led17_g: 1
+      led17_r: 1
+
+uart:
+  port: "auto"
+  baudrate: 115200
+  clock_freq: 100000000
\ No newline at end of file
diff --git a/test/api_gen/invalid_configs/2_mangled_yaml.yaml b/test/api_gen/invalid_configs/2_mangled_yaml.yaml
new file mode 100644
index 0000000..9386d37
--- /dev/null
+++ b/test/api_gen/invalid_configs/2_mangled_yaml.yaml
@@ -0,0 +1,26 @@
+---
+cores:
+  my_io_core:
+    type: io
+
+    inputs:
+      btnu: 1
+      btnd: 1
+      btnl: 1
+      btnr: 1
+      btnc: randomstringthatsnotaninteger 
+      sw: 16
+
+    outputs:
+      led: 16
+      led16_b: 1
+      led16_g: 1
+      led16_r: 1
+      led17_b: 1
+      led17_g: 1
+      led17_r: 1
+
+uart:
+  port: "auto"
+  baudrate: 115200
+  clock_freq: 100000000
\ No newline at end of file
diff --git a/test/api_gen/run_test.py b/test/api_gen/run_test.py
index a0b7ca4..366797a 100644
--- a/test/api_gen/run_test.py
+++ b/test/api_gen/run_test.py
@@ -1 +1,46 @@
-# try to build manta instances from valid and invalid configuration files
\ No newline at end of file
+# try to build manta instances from valid and invalid configuration files
+
+from os import listdir
+from os.path import isfile
+from manta import Manta
+
+
+# Valid Configurations
+
+print(" ==== Testing valid configurations ====")
+valid_configs_path = 'test/api_gen/valid_configs/'
+for config_file in sorted(listdir(valid_configs_path)):
+    caught_exception = None
+    try:
+        m = Manta(valid_configs_path + config_file)
+    
+    except Exception as e:
+        caught_exception = e
+        
+    if caught_exception is None:
+        print(f" -> config file {config_file} raised no exceptions.")
+    
+    else:
+        raise RuntimeError(f"Configuration {config_file} shouldn't have raised an exception, but raised  {caught_exception}")
+
+
+
+print('\n')
+
+# Invalid Configurations
+
+print(" ==== Testing invalid configurations ====")
+invalid_configs_path = 'test/api_gen/invalid_configs/'
+for config_file in sorted(listdir(invalid_configs_path)):
+    caught_exception = None
+    try:
+        m = Manta(invalid_configs_path + config_file)
+    
+    except Exception as e:
+        caught_exception = e
+
+    if caught_exception is not None: 
+        print(f" -> config file {config_file} raised the following exception:  {caught_exception}")
+    
+    else:
+        raise RuntimeError(f"Configuration {config_file} should have raised an exception, but did not!")