{title:'Fluent Assertions', created:'9.0.0'}

The juneau-assertions module in Juneau is a powerful API for performing fluent style assertions.

Fluent assertions have two types of methods:

- "asX" methods which perform transformations.
- "isX" methods which perform assertions.

Multiple transformations and assertions can be performed per statement.

##### Examples:

| import static org.apache.juneau.assertions.Assertions.*; | import static org.apache.juneau.assertions.AssertionPredicates.*; | | // Check the contents of a string. | assertString("foo, bar") | .asSplit(",") | .asTrimmed() | .is("foo", "bar"); | | // Extract a subset of properties from a list of beans and compare using Simplified JSON. | List<MyBean> myListOfBeans = ...; | assertBeanList(myListOfBeans) | .asPropertyMaps("a,b") | .asJson().is("[{a:1,b:'foo'}]"); | | // Perform an arbitrary Predicate check against a bean. | MyBean myBean = ...; | assertBean(myBean) | .is(x -> isValidCheck(x)) | | // Check that a list of strings has less than 10 entries and the first | // 3 entries are [foo, bar*, null] using assertion predicates. | List<String> myListOfStrings = ...; | assertStringList(myListOfStrings) | .asSize().isLt(10) | .asFirst(3) | .is(eq("foo"),match("bar*"),isNull()) | | // Check that an exception is thrown and is the specified type and has the specified message. | assertThrown(()->myBean.runBadMethod()) | .isExists() | .isExactType(RuntimeException. class) | .asMessage().is("foo");

The Assertions APIs are used throughout the REST client and server APIs for performing inline assertions on REST requests and responses.

##### Example:

| // Create a basic REST client with JSON support and download a bean. | MyBean bean = RestClient. create() | .json5() | .build() | .get(URI) | .run() | .assertStatus().asCode().is(200) | .assertHeader("Content-Type").isMatches("application/json*") | .getContent().assertValue().asString().isContains("OK") | .getContent().as(MyBean. class);

- Fluent Assertions for more information.