Unit tests

Valhalla currently uses GoogleTest for unit testing.

• The basics are covered in GoogleTest primer
• More advanced topics are covered here

Important things to note:

• EXPECT_XXX macros mark the test as failed but continue execution
  • Allows to test more at once
  • A preferred way over ASSERT_XXX
  • ASSERT_XXX family should be used when it's pointless to continue the test
    • e.g. the method we test returns nullptr instead of a valid pointer
• Tests execution order is unspecified
  • If the order is needed fixtures or test suite environments may help
  • Sometimes it may hint the test design needs rethinking
• Be careful with _ in test names - gtest joins a suite name with test name using _
  • TEST(Foo, Basic_test) and TEST(Foo_Basic, test) will produce a conflict
  • In practice it never happens - no need to worry much about it
• Be aware of curly braces {} inside macros
  • A typical case -> container with initializer list creation inside assert macro
  • Preprocessor is dumb and thinks commas separate the arguments
  • ASSERT_EQ(foo, vector{1,2,3});
  • Fixing this can be done by adding () - ASSERT_EQ(foo, (vector{1,2,3}));
• Disabling a test is easy - just prefix its name with DISABLED_
  • TEST(PredictiveTraffic, DISABLED_test_predictive_traffic)
  • They are still compiled and there is always a warning each time the suite runs