handle nonzero return codes

procs.py

@@ -9,6 +9,7 @@ class Process(object):
         self.environ = {}
         self.cwd = None
         self._stdout = None
+        self._returncode = None
 
 
     def set_command(self, command):
@@ -39,7 +40,8 @@ class Process(object):
 
     @property
     def returncode(self):
-        return 0
+        if self._returncode is not None:
+            return self._returncode
 
     def run(self):
         self._subprocess = subprocess.Popen(
@@ -48,7 +50,7 @@ class Process(object):
             stdin=subprocess.PIPE,
             stdout=subprocess.PIPE,
         )
-        self._subprocess.wait()
+        self._returncode = self._subprocess.wait()
         self._stdout = self._subprocess.stdout.read().decode()
 
 

tests/test_procs.py

@@ -14,3 +14,11 @@ def test_single_proc():
     assert ls.returncode == 0
     assert ls.stdout == u'file1\nfile2\nfile3\n'
 
+
+def test_returncode():
+    assert not os.path.exists('/bin/nosuchcommand')
+
+    p = Process('/bin/nosuchcommand')
+    p.run()
+    assert p.returncode == 127
+