diff --git a/Makefile b/Makefile
index 4f8488e..f20f609 100644
--- a/Makefile
+++ b/Makefile
@@ -8,6 +8,12 @@ ext:
 	python setup.py build_ext --inplace
 
 test:
+	make clean
+	@echo ""
+	@echo "[Test with py_common]"
+	python -m pytest tests
+	@echo ""
+	@echo "[Test with c_common]"
 	python setup.py build_ext --inplace
 	python -m pytest tests
 
diff --git a/tests/test_c_common.py b/tests/test_c_common.py
index 4d14034..7b703d6 100644
--- a/tests/test_c_common.py
+++ b/tests/test_c_common.py
@@ -1,62 +1,60 @@
-from pyModeS import c_common
-
-
-def test_conversions():
-    assert c_common.hex2bin("6E") == "01101110"
-    assert c_common.bin2hex("01101110") == "6E"
-    assert c_common.bin2hex("1101110") == "6E"
-
-
-def test_crc_decode():
-
-    assert c_common.crc("8D406B902015A678D4D220AA4BDA") == 0
-    assert c_common.crc("8d8960ed58bf053cf11bc5932b7d") == 0
-    assert c_common.crc("8d45cab390c39509496ca9a32912") == 0
-    assert c_common.crc("8d74802958c904e6ef4ba0184d5c") == 0
-    assert c_common.crc("8d4400cd9b0000b4f87000e71a10") == 0
-    assert c_common.crc("8d4065de58a1054a7ef0218e226a") == 0
-
-    assert c_common.crc("c80b2dca34aa21dd821a04cb64d4") == 10719924
-    assert c_common.crc("a800089d8094e33a6004e4b8a522") == 4805588
-    assert c_common.crc("a8000614a50b6d32bed000bbe0ed") == 5659991
-    assert c_common.crc("a0000410bc900010a40000f5f477") == 11727682
-    assert c_common.crc("8d4ca251204994b1c36e60a5343d") == 16
-    assert c_common.crc("b0001718c65632b0a82040715b65") == 353333
-
-
-def test_crc_encode():
-    parity = c_common.crc("8D406B902015A678D4D220AA4BDA", encode=True)
-    assert parity == 11160538
-
-
-def test_icao():
-    assert c_common.icao("8D406B902015A678D4D220AA4BDA") == "406B90"
-    assert c_common.icao("A0001839CA3800315800007448D9") == "400940"
-    assert c_common.icao("A000139381951536E024D4CCF6B5") == "3C4DD2"
-    assert c_common.icao("A000029CFFBAA11E2004727281F1") == "4243D0"
-
-
-def test_modes_altcode():
-    assert c_common.altcode("A02014B400000000000000F9D514") == 32300
-
-
-def test_modes_idcode():
-    assert c_common.idcode("A800292DFFBBA9383FFCEB903D01") == "1346"
-
-
-def test_graycode_to_altitude():
-    assert c_common.gray2alt("00000000010") == -1000
-    assert c_common.gray2alt("00000001010") == -500
-    assert c_common.gray2alt("00000011011") == -100
-    assert c_common.gray2alt("00000011010") == 0
-    assert c_common.gray2alt("00000011110") == 100
-    assert c_common.gray2alt("00000010011") == 600
-    assert c_common.gray2alt("00000110010") == 1000
-    assert c_common.gray2alt("00001001001") == 5800
-    assert c_common.gray2alt("00011100100") == 10300
-    assert c_common.gray2alt("01100011010") == 32000
-    assert c_common.gray2alt("01110000100") == 46300
-    assert c_common.gray2alt("01010101100") == 50200
-    assert c_common.gray2alt("11011110100") == 73200
-    assert c_common.gray2alt("10000000011") == 126600
-    assert c_common.gray2alt("10000000001") == 126700
+try:
+    from pyModeS import c_common
+
+    def test_conversions():
+        assert c_common.hex2bin("6E") == "01101110"
+        assert c_common.bin2hex("01101110") == "6E"
+        assert c_common.bin2hex("1101110") == "6E"
+
+    def test_crc_decode():
+
+        assert c_common.crc("8D406B902015A678D4D220AA4BDA") == 0
+        assert c_common.crc("8d8960ed58bf053cf11bc5932b7d") == 0
+        assert c_common.crc("8d45cab390c39509496ca9a32912") == 0
+        assert c_common.crc("8d74802958c904e6ef4ba0184d5c") == 0
+        assert c_common.crc("8d4400cd9b0000b4f87000e71a10") == 0
+        assert c_common.crc("8d4065de58a1054a7ef0218e226a") == 0
+
+        assert c_common.crc("c80b2dca34aa21dd821a04cb64d4") == 10719924
+        assert c_common.crc("a800089d8094e33a6004e4b8a522") == 4805588
+        assert c_common.crc("a8000614a50b6d32bed000bbe0ed") == 5659991
+        assert c_common.crc("a0000410bc900010a40000f5f477") == 11727682
+        assert c_common.crc("8d4ca251204994b1c36e60a5343d") == 16
+        assert c_common.crc("b0001718c65632b0a82040715b65") == 353333
+
+    def test_crc_encode():
+        parity = c_common.crc("8D406B902015A678D4D220AA4BDA", encode=True)
+        assert parity == 11160538
+
+    def test_icao():
+        assert c_common.icao("8D406B902015A678D4D220AA4BDA") == "406B90"
+        assert c_common.icao("A0001839CA3800315800007448D9") == "400940"
+        assert c_common.icao("A000139381951536E024D4CCF6B5") == "3C4DD2"
+        assert c_common.icao("A000029CFFBAA11E2004727281F1") == "4243D0"
+
+    def test_modes_altcode():
+        assert c_common.altcode("A02014B400000000000000F9D514") == 32300
+
+    def test_modes_idcode():
+        assert c_common.idcode("A800292DFFBBA9383FFCEB903D01") == "1346"
+
+    def test_graycode_to_altitude():
+        assert c_common.gray2alt("00000000010") == -1000
+        assert c_common.gray2alt("00000001010") == -500
+        assert c_common.gray2alt("00000011011") == -100
+        assert c_common.gray2alt("00000011010") == 0
+        assert c_common.gray2alt("00000011110") == 100
+        assert c_common.gray2alt("00000010011") == 600
+        assert c_common.gray2alt("00000110010") == 1000
+        assert c_common.gray2alt("00001001001") == 5800
+        assert c_common.gray2alt("00011100100") == 10300
+        assert c_common.gray2alt("01100011010") == 32000
+        assert c_common.gray2alt("01110000100") == 46300
+        assert c_common.gray2alt("01010101100") == 50200
+        assert c_common.gray2alt("11011110100") == 73200
+        assert c_common.gray2alt("10000000011") == 126600
+        assert c_common.gray2alt("10000000001") == 126700
+
+
+except:
+    pass