Fix #129: Add PSR-2 coding style checks to continuous integration tests

tests/script.sh

@@ -8,7 +8,7 @@ fi
 
 # Run tests.
 phpunit --version
-phpunit --configuration tests/phpunit.xml
+phpunit --configuration "tests/phpunit.xml"
 if [[ "${?}" -ne 0 ]]; then
     ((errors++))
 fi
@@ -112,4 +112,20 @@ if [[ ! -z "${elses}" ]]; then
     ((errors++))
 fi
 
+# Add composer bin directory to the path environment variable.
+export PATH="$PWD/vendor/bin:$PATH"
+
+# Detect coding standard violations.
+phpcs --version
+phpcs \
+    --extensions="php" \
+    --ignore="*/vendor/*" \
+    --standard="tests/ruleset.xml" \
+    -p \
+    -s \
+    .
+if [[ "${?}" -ne 0 ]]; then
+    ((errors++))
+fi
+
 exit "${errors}"