diff --git a/heavycomps/heavycomps/test/__init__.py b/heavycomps/heavycomps/test/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/heavycomps/heavycomps/test/test_uart.py b/heavycomps/heavycomps/test/test_uart.py
new file mode 100644
index 0000000..0177fd2
--- /dev/null
+++ b/heavycomps/heavycomps/test/test_uart.py
@@ -0,0 +1,41 @@
+import unittest
+
+from nmigen import *
+from nmigen.back.pysim import *
+
+from heavycomps import uart
+
+
+class Loopback:
+    def __init__(self, tuning_word=2**31):
+        self.tx = uart.RS232TX(tuning_word)
+        self.rx = uart.RS232RX(tuning_word)
+
+    def elaborate(self, platform):
+        m = Module()
+        m.submodules.tx = self.tx
+        m.submodules.rx = self.rx
+        m.d.comb += self.rx.rx.eq(self.tx.tx)
+        return m
+
+
+class TestUART(unittest.TestCase):
+    def test_loopback(self):
+        dut = Loopback()
+        test_vector = [32, 129, 201, 39, 0, 255]
+
+        with Simulator(Fragment.get(dut, None)) as sim:
+            sim.add_clock(1e-6)
+
+            def send():
+                for value in test_vector:
+                    yield from dut.tx.write(value)
+
+            def receive():
+                for value in test_vector:
+                    received = yield from dut.rx.read()
+                    self.assertEqual(received, value)
+
+            sim.add_sync_process(send)
+            sim.add_sync_process(receive)
+            sim.run()
diff --git a/heavycomps/heavycomps/uart.py b/heavycomps/heavycomps/uart.py
index b4195ba..522e3d5 100644
--- a/heavycomps/heavycomps/uart.py
+++ b/heavycomps/heavycomps/uart.py
@@ -1,6 +1,5 @@
 from nmigen import *
 from nmigen.lib.cdc import MultiReg
-from nmigen.cli import main
 
 
 class RS232RX:
@@ -50,6 +49,14 @@ class RS232RX:
 
         return m
 
+    def read(self):
+        while not (yield self.stb):
+            yield
+        value = yield self.data
+        # clear stb, otherwise multiple calls to this generator keep returning the same value
+        yield
+        return value
+
 
 class RS232TX:
     def __init__(self, tuning_word):
@@ -92,19 +99,10 @@ class RS232TX:
 
         return m
 
-
-class Loopback:
-    def elaborate(self, platform):
-        m = Module()
-        tuning_word = 2**31
-        tx = RS232TX(tuning_word)
-        rx = RS232RX(tuning_word)
-        m.submodules += tx, rx
-        m.d.comb += rx.rx.eq(tx.tx)
-        m.d.comb += tx.data.eq(42)
-        m.d.comb += tx.stb.eq(1)
-        return m
-
-if __name__ == "__main__":
-    uart = Loopback()
-    main(uart)
+    def write(self, data):
+        yield self.stb.eq(1)
+        yield self.data.eq(data)
+        yield
+        while not (yield self.ack):
+            yield
+        yield self.stb.eq(0)