brewv

#!/bin/bash
#
# Installs the previous version of a Homebrew formula
#
# Usage: brewv formula_name desired_version
#
# Based on http://stackoverflow.com/questions/3987683/homebrew-install-specific-version-of-formula#9832084
#
# Author:	Matti Schneider <hi@mattischneider.fr> (http://mattischneider.fr)

versions=$(brew versions $1)
result=$(echo "$versions" | grep -m 1 $2) #-m 1 to stop as soon as possible

if [[ $? = 0 ]]
then
	commit=$(echo $result | cut -d ' ' -f 4)
	formula=$(echo $result | cut -d ' ' -f 5)
	
	cd /usr/local
	if [[ -e $formula ]]
	then brew unlink $1	# will fail if not already installed, hence the check above
	fi
	git checkout $commit $formula &&
	brew install $1 &&
	git reset HEAD $formula &&
	git checkout -- $formula
	cd - > /dev/null
	echo "$1 $2 installed."
	echo "You can now switch versions with 'brew switch $1 <version>'"
else
	echo "$versions"
	echo
	echo "No version matching '$2' for '$1'"
	echo "Available versions have been printed above"
	exit 1
fi

Solution

Download this gist by Matti Schneider and check it into your repository.
(Note: you might need to make it executable: chmod +x brewv.)

In .travis.yml, include:
script:

• ./brewv xctool 0.1.7
• brew switch xctool 0.1.7
• xctool test -workspace YourWorkspace.xcworkspace -scheme YourTestScheme -sdk iphonesimulator7.0
  This will switch to an older version of xctool that is capable of running your test suite.

Keep on testing!
from https://coderwall.com/p/0gnk1a