[tests] Purge tests and start with a clean implementation of subprocess

Seems like subprocess and friends (Popen, communicate) are not so easy
to mock cleanly. Therefore, start from scratch and carefully write test
by test, until (at least) the old test coverage has been restored.

tests/test_util.py

@@ -1,18 +1,27 @@
 # pylint: disable=C0103,C0111
 
+import mock
 import unittest
 
+import mocks
+
 from bumblebee.util import *
 
 class TestUtil(unittest.TestCase):
+    def setUp(self):
+        self.popen = mocks.MockPopen("bumblebee.util")
+        self.some_command_with_args = "sample-command -a -b -c"
+        self.some_utf8 = "some string".encode("utf-8")
+
+    def tearDown(self):
+        self.popen.cleanup()
+
     def test_bytefmt(self):
-        value = 10
-        display = 10
-        units = [ "B", "KiB", "MiB", "GiB" ]
-        for unit in units:
-            self.assertEquals(bytefmt(value), "{:.2f}{}".format(display, unit))
-            value *= 1024
-        self.assertEquals(bytefmt(value), "{:.2f}GiB".format(display*1024))
+        self.assertEquals(bytefmt(10), "10.00B")
+        self.assertEquals(bytefmt(15*1024), "15.00KiB")
+        self.assertEquals(bytefmt(20*1024*1024), "20.00MiB")
+        self.assertEquals(bytefmt(22*1024*1024*1024), "22.00GiB")
+        self.assertEquals(bytefmt(35*1024*1024*1024*1024), "35840.00GiB")
 
     def test_durationfmt(self):
         self.assertEquals(durationfmt(00), "00:00")
@@ -22,4 +31,20 @@ class TestUtil(unittest.TestCase):
         self.assertEquals(durationfmt(3600), "01:00:00")
         self.assertEquals(durationfmt(7265), "02:01:05")
 
+    def test_execute(self):
+        execute(self.some_command_with_args)
+        self.assertTrue(self.popen.mock.popen.called)
+        self.popen.mock.popen.assert_call(self.some_command_with_args)
+        self.assertTrue(self.popen.mock.communicate.called)
+
+    def test_execute_utf8(self):
+        self.popen.mock.communicate.return_value = [ self.some_utf8, None ]
+        self.test_execute()
+
+    def test_execute_error(self):
+        self.popen.mock.returncode = 1
+
+        with self.assertRaises(RuntimeError):
+            execute(self.some_command_with_args)
+
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