Should I use Karate or Rest Assured for API testing?

It depends on what you want to optimize for. In short:

• Use Rest Assured if you want a Java-first, code-heavy API testing library with strong flexibility and easy integration into existing JUnit/TestNG test suites.
• Use Karate if you want a more readable DSL, built-in support for API, mocks, performance basics, and BDD-style tests, and you prefer writing less Java code.

Quick comparison

Rest Assured

Best for:

• Teams already deep in Java
• Fine-grained control over requests/assertions
• Integration with JUnit 5/TestNG, Mockito, Spring, etc.
• Custom frameworks and reusable Java utilities

Pros:

• Very flexible
• Excellent for unit/integration-style API tests
• Strong Java ecosystem compatibility
• Easy to express complex assertions in code

Cons:

• More boilerplate
• Tests can get verbose
• You build more of the framework yourself

Karate

Best for:

• Faster authoring of API tests
• Teams that want readable test cases
• BDD-style collaboration with non-developers
• Combining API tests with mocks and some performance testing

Pros:

• Less code, more readable
• Built-in features reduce framework work
• Good for data-driven tests
• Helpful for contract-ish, acceptance-style API testing

Cons:

• DSL learning curve if you’re used to pure Java
• Less natural if your team wants everything in Java
• Can be awkward for very custom test logic

Rule of thumb

Choose Rest Assured if:

• Your team is mainly Java developers
• You want tests to feel like normal Java test code
• You need lots of custom logic and reusable helpers

Choose Karate if:

• You want fast, readable API test development
• You like BDD/Gherkin-like syntax
• You want built-in tooling to reduce setup work

My practical recommendation

• For a Java engineering team building a custom automation framework: Rest Assured
• For product-facing acceptance tests or a team that values readability and speed: Karate

If you tell me:

1. your language stack,
2. whether these are integration, contract, or end-to-end API tests,
3. team size and skill mix,

…I can recommend one more precisely.