add POC for behave

Check that we can test Fix with behave using pexpect

Author: arnemertz

behave/hello.feature

@@ -0,0 +1,6 @@
+Feature: starting Fix (behave initial setup)
+
+  Scenario: run the simple Hello World app that Fix is today
+    Given nothing
+    When we run Fix
+    Then it prints "Hello, fix!" and terminates

behave/steps/hello.py

@@ -0,0 +1,21 @@
+from behave import given, when, then
+import pexpect
+
+fix_executable = '../cmake-build-debug/bin/fix'
+
+
+@given(u'nothing')
+def nothing(context):
+    pass
+
+
+@when(u'we run Fix')
+def start_fix(context):
+    context.fix = pexpect.spawn(fix_executable)
+
+
+@then(u'it prints "{expected_output}" and terminates')
+def check_output(context, expected_output):
+    fix = context.fix
+    fix.expect_exact(expected_output)
+    assert (fix.wait() == 0)