diff --git a/src/zircon/tb/zircon_ip_len_cksum/test_zircon_ip_len_cksum.py b/src/zircon/tb/zircon_ip_len_cksum/test_zircon_ip_len_cksum.py
index 316fb99..7a57e3a 100644
--- a/src/zircon/tb/zircon_ip_len_cksum/test_zircon_ip_len_cksum.py
+++ b/src/zircon/tb/zircon_ip_len_cksum/test_zircon_ip_len_cksum.py
@@ -28,7 +28,6 @@ import pytest
 import cocotb
 from cocotb.clock import Clock
 from cocotb.triggers import RisingEdge
-from cocotb.regression import TestFactory
 
 from cocotbext.axi import AxiStreamBus, AxiStreamSource, AxiStreamSink, AxiStreamFrame
 
@@ -63,6 +62,7 @@ class TB:
         await RisingEdge(self.dut.clk)
 
 
+@cocotb.test()
 async def run_test(dut):
 
     tb = TB(dut)
@@ -225,12 +225,6 @@ async def run_test(dut):
     await RisingEdge(dut.clk)
 
 
-if getattr(cocotb, 'top', None) is not None:
-
-    factory = TestFactory(run_test)
-    factory.generate_tests()
-
-
 # cocotb-test
 
 tests_dir = os.path.abspath(os.path.dirname(__file__))
diff --git a/src/zircon/tb/zircon_ip_rx_parse/test_zircon_ip_rx_parse.py b/src/zircon/tb/zircon_ip_rx_parse/test_zircon_ip_rx_parse.py
index d7c66c5..90dc4c9 100644
--- a/src/zircon/tb/zircon_ip_rx_parse/test_zircon_ip_rx_parse.py
+++ b/src/zircon/tb/zircon_ip_rx_parse/test_zircon_ip_rx_parse.py
@@ -31,7 +31,6 @@ import cocotb_test.simulator
 import cocotb
 from cocotb.clock import Clock
 from cocotb.triggers import RisingEdge
-from cocotb.regression import TestFactory
 
 from cocotbext.axi import AxiStreamBus, AxiStreamSource, AxiStreamSink, AxiStreamFrame
 
@@ -123,6 +122,7 @@ class TB:
         await RisingEdge(self.dut.clk)
 
 
+@cocotb.test()
 async def run_test(dut):
 
     tb = TB(dut)
@@ -471,12 +471,6 @@ async def run_test(dut):
     await RisingEdge(dut.clk)
 
 
-if getattr(cocotb, 'top', None) is not None:
-
-    factory = TestFactory(run_test)
-    factory.generate_tests()
-
-
 # cocotb-test
 
 tests_dir = os.path.abspath(os.path.dirname(__file__))
diff --git a/src/zircon/tb/zircon_ip_tx_deparse/test_zircon_ip_tx_deparse.py b/src/zircon/tb/zircon_ip_tx_deparse/test_zircon_ip_tx_deparse.py
index c64d717..98ba8b9 100644
--- a/src/zircon/tb/zircon_ip_tx_deparse/test_zircon_ip_tx_deparse.py
+++ b/src/zircon/tb/zircon_ip_tx_deparse/test_zircon_ip_tx_deparse.py
@@ -29,7 +29,6 @@ import cocotb_test.simulator
 import cocotb
 from cocotb.clock import Clock
 from cocotb.triggers import RisingEdge
-from cocotb.regression import TestFactory
 
 from cocotbext.axi import AxiStreamBus, AxiStreamSource, AxiStreamSink, AxiStreamFrame
 
@@ -116,6 +115,7 @@ class TB:
         await RisingEdge(self.dut.clk)
 
 
+@cocotb.test()
 async def run_test(dut):
 
     tb = TB(dut)
@@ -328,12 +328,6 @@ async def run_test(dut):
     await RisingEdge(dut.clk)
 
 
-if getattr(cocotb, 'top', None) is not None:
-
-    factory = TestFactory(run_test)
-    factory.generate_tests()
-
-
 # cocotb-test
 
 tests_dir = os.path.abspath(os.path.dirname(__file__))