Use Plain JUnit5 for advanced test assertions
Context and Problem Statement
How to write readable test assertions? How to write readable test assertions for advanced tests?
Considered Options
- Plain JUnit5
- Hamcrest
- AssertJ
Decision Outcome
Chosen option: “Plain JUnit5”, because comes out best (see below).
Positive Consequences
- Tests are more readable
- More easy to write tests
- More readable assertions
Negative Consequences
- More complicated testing leads to more complicated assertions
Pros and Cons of the Options
Plain JUnit5
Homepage:https://junit.org/junit5/docs/current/user-guide/ JabRef testing guidelines: <../testing.md>
Example:
Stringactual=markdownFormatter.format(source);assertTrue(actual.contains("Markup<br />"));assertTrue(actual.contains("<li>list item one</li>"));assertTrue(actual.contains("<li>list item 2</li>"));assertTrue(actual.contains("> rest"));assertFalse(actual.contains("\n"));- Good, because Junit5 is “common Java knowledge”
- Bad, because complex assertions tend to get hard to read
- Bad, because no fluent API
Hamcrest
Homepage:https://github.com/hamcrest/JavaHamcrest
- Good, because offers advanced matchers (such as
contains) - Bad, because not full fluent API
- Bad, because entry barrier is increased
AssertJ
Homepage:https://joel-costigliola.github.io/assertj/
Example:
assertThat(markdownFormatter.format(source)).contains("Markup<br />").contains("<li>list item one</li>").contains("<li>list item 2</li>").contains("> rest").doesNotContain("\n");- Good, because offers fluent assertions
- Good, because allows partial string testing to focus on important parts
- Good, because assertions are more readable
- Bad, because not commonly used
- Bad, because newcomers have to learn an additional language to express test cases
- Bad, because entry barrier is increased
- Bad, because expressions of test cases vary from unit test to unit test
Links
- German comparison between Hamcrest and AssertJ:https://www.sigs-datacom.de/uploads/tx_dmjournals/philipp_JS_06_15_gRfN.pdf