add a naive Babel plugin that can be used by integration tests

test/fixture/babel-plugin-test-doubler.js

@@ -0,0 +1,46 @@
+/*
+ A Babel plugin that causes each AVA test to be duplicated with a new title.
+
+     test('foo', t => {});
+
+ becomes
+
+     test('foo', t => {});
+     test('repeated test: foo', t => {});
+
+  This is used by some integration tests to validate correct handling of Babel config options.
+*/
+
+function plugin(babel) {
+	var t = babel.types;
+	var anonCount = 1;
+
+	return {
+		visitor: {
+			CallExpression: function (path) {
+				var node = path.node;
+				var callee = node.callee;
+				var args = node.arguments;
+				if (callee.type === 'Identifier' && callee.name === 'test') {
+					if (args.length === 1) {
+						args = [t.StringLiteral('repeated test: anonymous' + anonCount++), args[0]];
+					} else if (args.length === 2 && args[0].type === 'StringLiteral') {
+						if (/^repeated test/.test(args[0].value)) {
+							return;
+						}
+						args = args.slice();
+						args[0] = t.StringLiteral('repeated test: ' + args[0].value);
+					} else {
+						throw new Error('the plugin does not know how to handle this call to test');
+					}
+					path.insertAfter(t.CallExpression(
+						t.Identifier('test'),
+						args
+					));
+				}
+			}
+		}
+	};
+}
+
+module.exports = plugin;