diff --git a/readthedocs/config/tests/test_validation.py b/readthedocs/config/tests/test_validation.py
new file mode 100644
index 00000000000..5325aab3f62
--- /dev/null
+++ b/readthedocs/config/tests/test_validation.py
@@ -0,0 +1,161 @@
+# -*- coding: utf-8 -*-
+from __future__ import division, print_function, unicode_literals
+
+import os
+
+from mock import patch
+from pytest import raises
+from six import text_type
+
+from readthedocs.config.validation import (
+    INVALID_BOOL, INVALID_CHOICE, INVALID_DIRECTORY, INVALID_FILE, INVALID_LIST,
+    INVALID_PATH, INVALID_STRING, ValidationError, validate_bool,
+    validate_choice, validate_directory, validate_file, validate_list,
+    validate_path, validate_string)
+
+
+def describe_validate_bool():
+    def it_accepts_true():
+        assert validate_bool(True) is True
+
+    def it_accepts_false():
+        assert validate_bool(False) is False
+
+    def it_accepts_0():
+        assert validate_bool(0) is False
+
+    def it_accepts_1():
+        assert validate_bool(1) is True
+
+    def it_fails_on_string():
+        with raises(ValidationError) as excinfo:
+            validate_bool('random string')
+        assert excinfo.value.code == INVALID_BOOL
+
+
+def describe_validate_choice():
+
+    def it_accepts_valid_choice():
+        result = validate_choice('choice', ('choice', 'another_choice'))
+        assert result is 'choice'
+
+        with raises(ValidationError) as excinfo:
+            validate_choice('c', 'abc')
+        assert excinfo.value.code == INVALID_LIST
+
+    def it_rejects_invalid_choice():
+        with raises(ValidationError) as excinfo:
+            validate_choice('not-a-choice', ('choice', 'another_choice'))
+        assert excinfo.value.code == INVALID_CHOICE
+
+
+def describe_validate_list():
+
+    def it_accepts_list_types():
+        result = validate_list(['choice', 'another_choice'])
+        assert result == ['choice', 'another_choice']
+
+        result = validate_list(('choice', 'another_choice'))
+        assert result == ['choice', 'another_choice']
+
+        def iterator():
+            yield 'choice'
+
+        result = validate_list(iterator())
+        assert result == ['choice']
+
+        with raises(ValidationError) as excinfo:
+            validate_choice('c', 'abc')
+        assert excinfo.value.code == INVALID_LIST
+
+    def it_rejects_string_types():
+        with raises(ValidationError) as excinfo:
+            result = validate_list('choice')
+        assert excinfo.value.code == INVALID_LIST
+
+
+def describe_validate_directory():
+
+    def it_uses_validate_path(tmpdir):
+        patcher = patch('readthedocs.config.validation.validate_path')
+        with patcher as validate_path:
+            path = text_type(tmpdir.mkdir('a directory'))
+            validate_path.return_value = path
+            validate_directory(path, str(tmpdir))
+            validate_path.assert_called_with(path, str(tmpdir))
+
+    def it_rejects_files(tmpdir):
+        tmpdir.join('file').write('content')
+        with raises(ValidationError) as excinfo:
+            validate_directory('file', str(tmpdir))
+        assert excinfo.value.code == INVALID_DIRECTORY
+
+
+def describe_validate_file():
+
+    def it_uses_validate_path(tmpdir):
+        patcher = patch('readthedocs.config.validation.validate_path')
+        with patcher as validate_path:
+            path = tmpdir.join('a file')
+            path.write('content')
+            path = str(path)
+            validate_path.return_value = path
+            validate_file(path, str(tmpdir))
+            validate_path.assert_called_with(path, str(tmpdir))
+
+    def it_rejects_directories(tmpdir):
+        tmpdir.mkdir('directory')
+        with raises(ValidationError) as excinfo:
+            validate_file('directory', str(tmpdir))
+        assert excinfo.value.code == INVALID_FILE
+
+
+def describe_validate_path():
+
+    def it_accepts_relative_path(tmpdir):
+        tmpdir.mkdir('a directory')
+        validate_path('a directory', str(tmpdir))
+
+    def it_accepts_files(tmpdir):
+        tmpdir.join('file').write('content')
+        validate_path('file', str(tmpdir))
+
+    def it_accepts_absolute_path(tmpdir):
+        path = str(tmpdir.mkdir('a directory'))
+        validate_path(path, 'does not matter')
+
+    def it_returns_absolute_path(tmpdir):
+        tmpdir.mkdir('a directory')
+        path = validate_path('a directory', str(tmpdir))
+        assert path == os.path.abspath(path)
+
+    def it_only_accepts_strings():
+        with raises(ValidationError) as excinfo:
+            validate_path(None, '')
+        assert excinfo.value.code == INVALID_STRING
+
+    def it_rejects_non_existent_path(tmpdir):
+        with raises(ValidationError) as excinfo:
+            validate_path('does not exist', str(tmpdir))
+        assert excinfo.value.code == INVALID_PATH
+
+
+def describe_validate_string():
+
+    def it_accepts_unicode():
+        result = validate_string(u'Unicöde')
+        assert isinstance(result, text_type)
+
+    def it_accepts_nonunicode():
+        result = validate_string('Unicode')
+        assert isinstance(result, text_type)
+
+    def it_rejects_float():
+        with raises(ValidationError) as excinfo:
+            validate_string(123.456)
+        assert excinfo.value.code == INVALID_STRING
+
+    def it_rejects_none():
+        with raises(ValidationError) as excinfo:
+            validate_string(None)
+        assert excinfo.value.code == INVALID_STRING
diff --git a/readthedocs/config/validation.py b/readthedocs/config/validation.py
new file mode 100644
index 00000000000..b317612dd2c
--- /dev/null
+++ b/readthedocs/config/validation.py
@@ -0,0 +1,99 @@
+"""Validations for the RTD configuration file."""
+from __future__ import division, print_function, unicode_literals
+
+import os
+
+from six import string_types, text_type
+
+INVALID_BOOL = 'invalid-bool'
+INVALID_CHOICE = 'invalid-choice'
+INVALID_LIST = 'invalid-list'
+INVALID_DIRECTORY = 'invalid-directory'
+INVALID_FILE = 'invalid-file'
+INVALID_PATH = 'invalid-path'
+INVALID_STRING = 'invalid-string'
+
+
+class ValidationError(Exception):
+
+    """Base error for validations."""
+
+    messages = {
+        INVALID_BOOL: 'expected one of (0, 1, true, false), got {value}',
+        INVALID_CHOICE: 'expected one of ({choices}), got {value}',
+        INVALID_DIRECTORY: '{value} is not a directory',
+        INVALID_FILE: '{value} is not a file',
+        INVALID_PATH: 'path {value} does not exist',
+        INVALID_STRING: 'expected string',
+        INVALID_LIST: 'expected list',
+    }
+
+    def __init__(self, value, code, format_kwargs=None):
+        self.value = value
+        self.code = code
+        defaults = {
+            'value': value,
+        }
+        if format_kwargs is not None:
+            defaults.update(format_kwargs)
+        message = self.messages[code].format(**defaults)
+        super(ValidationError, self).__init__(message)
+
+
+def validate_list(value):
+    """Check if ``value`` is an iterable."""
+    if isinstance(value, str):
+        raise ValidationError(value, INVALID_LIST)
+    if not hasattr(value, '__iter__'):
+        raise ValidationError(value, INVALID_LIST)
+    return list(value)
+
+
+def validate_choice(value, choices):
+    """Check that ``value`` is in ``choices``."""
+    choices = validate_list(choices)
+    if value not in choices:
+        raise ValidationError(value, INVALID_CHOICE, {
+            'choices': ', '.join(map(str, choices))
+        })
+    return value
+
+
+def validate_bool(value):
+    """Check that ``value`` is an boolean value."""
+    if value not in (0, 1, False, True):
+        raise ValidationError(value, INVALID_BOOL)
+    return bool(value)
+
+
+def validate_directory(value, base_path):
+    """Check that ``value`` is a directory."""
+    path = validate_path(value, base_path)
+    if not os.path.isdir(path):
+        raise ValidationError(value, INVALID_DIRECTORY)
+    return path
+
+
+def validate_file(value, base_path):
+    """Check that ``value`` is a file."""
+    path = validate_path(value, base_path)
+    if not os.path.isfile(path):
+        raise ValidationError(value, INVALID_FILE)
+    return path
+
+
+def validate_path(value, base_path):
+    """Check that ``value`` is an existent file in ``base_path``."""
+    string_value = validate_string(value)
+    pathed_value = os.path.join(base_path, string_value)
+    final_value = os.path.abspath(pathed_value)
+    if not os.path.exists(final_value):
+        raise ValidationError(value, INVALID_PATH)
+    return final_value
+
+
+def validate_string(value):
+    """Check that ``value`` is a string type."""
+    if not isinstance(value, string_types):
+        raise ValidationError(value, INVALID_STRING)
+    return text_type(value)
diff --git a/readthedocs/rtd_tests/tests/test_build_config.py b/readthedocs/rtd_tests/tests/test_build_config.py
index 73419c5cf48..11afa046711 100644
--- a/readthedocs/rtd_tests/tests/test_build_config.py
+++ b/readthedocs/rtd_tests/tests/test_build_config.py
@@ -5,7 +5,7 @@
 import pytest
 import six
 import yamale
-from readthedocs_build.testing import utils
+from readthedocs.config.tests import utils
 from yamale.validators import DefaultValidators, Validator
 
 V2_SCHEMA = path.join(
diff --git a/requirements/testing.txt b/requirements/testing.txt
index 786f2070276..d742a8f4c7f 100644
--- a/requirements/testing.txt
+++ b/requirements/testing.txt
@@ -2,8 +2,11 @@
 
 django-dynamic-fixture==2.0.0
 
-pytest<4,>=3.3.2
+# 3.6.1 and >3.2.5 is incompatible
+# with pytest-describe 0.11.0
+pytest==3.2.5
 pytest-django==3.1.2
+pytest-describe==0.11.0
 pytest-xdist==1.22.0
 apipkg==1.4
 execnet==1.5.0