tox.ini: pin versions and test latest

Author: spookylukey

fluent.runtime/setup.py

@@ -19,6 +19,7 @@
           'Programming Language :: Python :: 3.5',
       ],
       packages=['fluent', 'fluent.runtime'],
+      # These should also be duplicated in tox.ini
       install_requires=[
           'fluent.syntax>=0.10,<=0.13',
           'attrs',

fluent.runtime/tox.ini

@@ -1,10 +1,28 @@
 [tox]
-envlist = py27, py35, py36, py37, pypy, pypy3
+envlist = {py27, py35, py36, py37, pypy, pypy3}-syntax0.12, py36-syntax0.10, latest
 skipsdist=True
 
 [testenv]
 setenv =
     PYTHONPATH = {toxinidir}
 deps =
-     .
+     attrs==19.1.0
+     babel==2.6.0
+     pytz==2018.9
+     six==1.12.0
+     syntax0.10: fluent.syntax==0.10.0
+     syntax0.12: fluent.syntax==0.12.0
 commands = ./runtests.py
+
+[testenv:latest]
+basepython = python3.6
+deps =
+     # Here we try to reproduce what a user gets if they do 'pip install fluent.runtime'
+     # It's tempting to use '.' here to get 'pip install .'
+     # Unfortunately it is super slow: https://github.com/pypa/pip/issues/2195
+     # Instead we define the same requirements as in setup.py
+     fluent.syntax>=0.10,<=0.13
+     attrs
+     babel
+     pytz
+     six