config: use '//' for Python 3 (instead of '/')

amodem/config.py

@@ -51,7 +51,7 @@ class Configuration(object):
         ])
 
         # QAM constellation
-        Nx = 2 ** int(np.ceil(bits_per_symbol / 2))
+        Nx = 2 ** int(np.ceil(bits_per_symbol // 2))
         Ny = self.Npoints // Nx
         symbols = [complex(x, y) for x in range(Nx) for y in range(Ny)]
         symbols = np.array(symbols)

amodem/tests/test_configs.py

@@ -4,3 +4,9 @@ from amodem import config
 def test_bitrates():
     for rate, cfg in sorted(config.bitrates.items()):
         assert rate * 1000 == cfg.modem_bps
+
+
+def test_slowest():
+    c = config.slowest()
+    assert c.Npoints == 2
+    assert list(c.symbols) == [-1j, 1j]