Merge pull request #289 from wp-cli/fix/use-version-range-for-tests-dependency

Use version range for `wp-cli/wp-cli-tests` dependency

Author: schlessera

composer.json

@@ -16,7 +16,7 @@
     },
     "require-dev": {
         "wp-cli/extension-command": "^1.2 || ^2",
-        "wp-cli/wp-cli-tests": "3.0.11"
+        "wp-cli/wp-cli-tests": "^3.0.11"
     },
     "config": {
         "process-timeout": 7200,