Providence Utils: Testing

The providence-testing library is meant for helping with testing related to providence, and comparing providence messages.

Comparing And Matching

There are 3 notable hamcrest matchers added in the testing library. These are available through static methods on ProvidenceMatchers:

• equalToMessage(expected): Checks if two messages is equal. This is essentially the same as equals(value), but with different output on failure. Instead of just displaying the two messages' toString() output it tried to generate a field-by-field diff.

• hasFieldValue(path): Checks that the value at the given path is present. So a short-hand (with better output) of checking the specified field. To these two checks the same, just that the last has better failure output: java assertTrue(msg.getMyField().hasOtherField()); assertThat(msg.getMyField().hasOtherField(), is(true)); assertThat(msg, hasFieldValue("my_field.other_field"));

• hasFieldValueThat(path, matcher): Uses the same depth checking as hasFieldValue, but also takes a matcher to match against the actual value. So these would be equivalent, but one with better failure output: java assertThat(msg.getMyField().getOtherField(), startsWith("boo.")); assertThat(msg, hasFieldValueThat("my_field.other_field", startsWith("boo.")));

Generating Messages for Testing

There is also added a message generator that can be handled with a junit @Rule. The MessageGenerator can generate and fill message either with totally random data, or using special rules, the generator watcher is a simple wrapper that handles multiple message generators, setting up default generators and keeping messages in case of failure.

class MyTest {
    @Rule
    SimpleGeneratorWatcher generator = SimpleGeneratorWatcher
            .create()
            .dumpOnFailure()
            .withGenerator(MyMessage.kDescriptor, gen -> {
                gen.setValueGenerator(MyMessage._Field.UUID,
                        ctx -> UUID.randomUUID().toString());
            });

    @Test
    public testSomething() {
        generator.withGenerator(MyMessage.kDescriptor, gen -> {
            gen.setValueGenerator(MyMessage._Field.NAME,
                    ctx -> ctx.getFairy().person().getFullName());
            gen.setValueGenerator(MyMessage._Field.AGE,
                    ctx -> 20 + ctx.getRandom().nextInt(35));
        });

        MyMessage msg = generator.generate(MyMessage.kDescriptor);
        sut.doSomething(msg);

        assertThat(sut.state(), is(SystemUnderTest.CORRECT));
    }
}