REST Assured provides the HTTP DSL; TestNG/JUnit provide test structure, lifecycle (setup/teardown), grouping, parallelism, and reporting. Data providers enable data-driven API tests.
You put REST Assured calls inside @Test methods, use @BeforeClass/@BeforeMethod for base URI/auth setup, and @AfterClass for cleanup. TestNG's @DataProvider (or JUnit 5's @ParameterizedTest) feeds many input sets into one test — data-driven testing for validating multiple payloads, boundary values, or negative cases. TestNG groups (@Test(groups='smoke')) and parallel execution scale the suite, and listeners/Allure produce reports. This separation — framework for orchestration, REST Assured for HTTP — is how production API suites are built, and a common design question.
A @DataProvider supplies ten (payload, expectedStatus) pairs to one @Test that POSTs each and asserts the status — covering valid, boundary, and invalid inputs without duplicating the test method.
You need to test a create endpoint against 15 different payloads (valid and invalid). What's the maintainable structure?