add feature file for basic CLI behavior

Before I implement behavior with expected input, I want to have graceful
behavior with wrong input. Also remove the existing check for the hello
world behavior

Author: arnemertz

behave/fix_cli.feature

@@ -0,0 +1,24 @@
+Feature: Fix CLI behavior
+
+  Scenario: Show usage when called without arguments
+    When we call Fix without arguments
+    Then it prints usage information
+    And it prints a list of available commands
+    And terminates with exit code 1
+
+  Scenario: Show usage when called with help option
+    When we call Fix with argument list "--help"
+    Then it prints usage information
+    And it prints a list of available commands
+    And terminates with exit code 0
+
+
+  Scenario Outline: Show error when called with an unknown argument
+    When we call Fix with argument list "<args>"
+    Then it prints "fix: '<arg1>' is not a fix command. See 'fix --help'."
+    And terminates with exit code 1
+
+  Examples:
+      | args         | arg1  |
+      | foo          | foo   |
+      | bar baz      | bar   |

behave/hello.feature

@@ -0,0 +1,50 @@
+from behave import given, when, then
+import pexpect
+
+fix_executable = '../cmake-build-debug/bin/fix'
+
+
+@given(u'nothing')
+def nothing(context):
+    pass
+
+
+def _start_fix_with_args(context, args):
+    context.fix = pexpect.spawn(fix_executable, args=args)
+
+
+@when(u'we call Fix with argument list "{args}"')
+def start_fix(context, args):
+    _start_fix_with_args(context, args.strip().split(" "))
+
+
+@when(u'we call Fix without arguments')
+def start_fix(context):
+    _start_fix_with_args(context, [])
+
+
+@then(u'it prints "{output}"')
+def check_output(context, output):
+    context.fix.expect_exact(output)
+
+
+@then(u'it prints usage information')
+def check_usage(context):
+    usage = "usage: fix [--help] <command> [<args>]"
+    check_output(usage)
+
+
+@then(u'it prints a list of available commands')
+def check_commands(context):
+    command_list = """Available commands:
+   create        Create a new issue
+   setstatus     Set the status of an issue
+   list          List all existing issues
+   show          Show a specific issue
+"""
+    check_output(command_list)
+
+
+@then(u'terminates with exit code {ec:d}')
+def check_output(context, ec):
+    assert (context.fix.wait() == ec)