fail when tests executed without cli

index.js

@@ -1,10 +1,24 @@
 'use strict';
 var setImmediate = require('set-immediate-shim');
 var hasFlag = require('has-flag');
+var relative = require('path').relative;
 var serializeError = require('serialize-error');
 var Runner = require('./lib/runner');
+var log = require('./lib/logger');
 var runner = new Runner();
 
+// check if the test is being run without AVA cli
+var isForked = typeof process.send === 'function';
+
+if (!isForked) {
+	var path = relative('.', process.argv[1]);
+
+	log.write();
+	log.error('Test files must be run with the AVA CLI:\n\n    $ ava ' + path + '\n');
+
+	process.exit(1);
+}
+
 // if fail-fast is enabled, use this variable to detect,
 // that no more tests should be logged
 var isFailed = false;