Detect duplicate recipe tests

unittests/test_test.py

 #!/usr/bin/env python
 # Copyright 2017 The LUCI Authors. All rights reserved.
 # Use of this source code is governed under the Apache License, Version 2.0
 # that can be found in the LICENSE file.
 
 import json
 import os
 import shutil
 import subprocess
 import sys
@@ skipping 1067 matching lines @@
     mw = RecipeModuleWriter(self._root_dir, 'foo_module')
     mw.test_methods['baz'] = ['pass']
     mw.write()
     mw.example.DEPS = ['foo_module']
     mw.example.GenTestsLines = ['api.foo_module.baz()', 'yield api.test("basic")']
     mw.example.add_expectation('basic')
     mw.example.write()
     self._run_recipes('test', 'run', '--json', self.json_path)
     self.assertEqual(self.json_generator.get(), self.json_contents)
 
+  def test_test_duplicate(self):
+    rw = RecipeWriter(os.path.join(self._root_dir, 'recipes'), 'foo')
+    rw.RunStepsLines = ['pass']
+    rw.GenTestsLines = ['yield api.test("basic")'] * 2
+    rw.add_expectation('basic')
+    rw.write()
+    with self.assertRaises(subprocess.CalledProcessError) as cm:
+      self._run_recipes('test', 'run')
+    self.assertIn(
+        'Exception: While generating results for \'foo\': '
+            'ValueError: Duplicate test found: basic',
+        cm.exception.output)
+
   def test_diff_basic(self):
     g1 = self.json_generator
     g2 = self.json_generator
     self._run_recipes(
         'test', 'diff',
         '--baseline', g1.write(),
         '--actual', g2.write(),
         '--json', self.json_path)
     self.assertEqual(self.json_generator.get(), self.json_contents)
 
@@ skipping 61 matching lines @@
             .check_failure('bar_check', 'bar_file', 2, 'bar_func', ['bar_args'])
             .internal_failure('bar_internal')
             .uncovered_module('bar_module')
             .unused_expectation('bar_expectation')
             .get(),
         self.json_contents)
 
 
 if __name__ == '__main__':
   sys.exit(unittest.main())