diff --git a/.travis.yml b/.travis.yml
index 15179ec992..84cd148900 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -35,15 +35,63 @@ before_install:
   fi
 before_script:
 - |
-  stable='^[0-9\.]+$';
+  # Remove Xdebug for a huge performance increase, but not from nightly or hhvm:
+  stable='^[0-9\.]+$'
   if [[ "$TRAVIS_PHP_VERSION" =~ $stable ]]; then
-      phpenv config-rm xdebug.ini
+    phpenv config-rm xdebug.ini
   fi
-- npm install -g npm
+- |
+  # Export Composer's global bin dir to PATH, but not on PHP 5.2:
+  if [[ ${TRAVIS_PHP_VERSION:0:3} != "5.2" ]]; then
+    composer config --list --global
+    export PATH=`composer config --list --global | grep '\[home\]' | { read a; echo "${a#* }/vendor/bin:$PATH"; }`
+  fi
+- |
+  # Install the specified version of PHPUnit depending on the PHP version:
+  if [[ "$WP_TRAVISCI" == "travis:phpunit" ]]; then
+    case "$TRAVIS_PHP_VERSION" in
+      7.1|7.0|hhvm|nightly)
+        echo "Using PHPUnit 5.7"
+        composer global require "phpunit/phpunit=5.7.*"
+        ;;
+      5.6|5.5|5.4|5.3)
+        echo "Using PHPUnit 4.8"
+        composer global require "phpunit/phpunit=4.8.*"
+        ;;
+      5.2)
+        # Do nothing, use default PHPUnit 3.6.x
+        echo "Using default PHPUnit, hopefully 3.6"
+        ;;
+      *)
+        echo "No PHPUnit version handling for PHP version $TRAVIS_PHP_VERSION"
+        exit 1
+        ;;
+    esac
+  fi
+- npm --version
+- node --version
+- nvm install 4.7.2
 - npm install -g grunt-cli
 - npm install
 - php --version
+- |
+  # Debug PHP extensions, but not on HHVM because the command hangs indefinitely:
+  if [[ "$TRAVIS_PHP_VERSION" != 'hhvm' ]]; then
+    php -m
+  fi
+- npm --version
+- node --version
+- which phpunit
+- phpunit --version
+- curl --version
+- grunt --version
+- git --version
+- svn --version
 script: grunt $WP_TRAVISCI
 notifications:
   slack:
-    secure: "ln2sC0yUOMzGGJ9PR56cxafCO2YSBQtFs0JuoSjvmXN0+jCGbQL781z2osEJ24BEl4o3zMLfiFPgieM7D+VuRObU6TiVFLmbebgoSyW/1Gs+jPNxBXPKOSLE3/4CV8ifyhm5XZr2xT6z8OWC6StHl2nPis4wZ91UHbj6FhlMyFM="
+    rooms:
+      secure: WuMCpfgrm0GIdPbYzsGOsakZ5x7QIbEBwD+CPHVXGKbL3ZbqQ+BVcDRnMiwzxjgf1vzg2de0taXCSMGKBxsWce23NZkOnmwPdIB8XOnwDV7T7zylgYD5S7p3gI6gV0l8Y3/gROdXFZap6viC1qRr4E79ow53RKk7E3WyOo7TWqo=
+    on_start: never
+    on_failure: always
+    on_success: change