CODEWITHSUNDEEP
javajunitassertassertions
Robert
Robert

Reputation: 8619

assert vs. JUnit Assertions

Today I saw a JUnit test case with a java assertion instead of the JUnit assertions—Are there significant advantages or disadvantages to prefer one over the other?

Upvotes: 110

Views: 45480

Answers (6)

Yishai
Yishai

Reputation: 91931

In JUnit4 the exception (actually Error) thrown by a JUnit assert is the same as the error thrown by the java assert keyword (AssertionError), so it is exactly the same as assertTrue and other than the stack trace you couldn't tell the difference.

That being said, asserts have to run with a special flag in the JVM, causing many tests to appear to pass just because someone forgot to configure the system with that flag when the JUnit tests were run - not good.

In general, because of this, I would argue that using the JUnit assertTrue is the better practice, because it guarantees the test is run, ensures consistency (you sometimes use assertThat or other asserts that are not a java keyword) and if the behavior of JUnit asserts should change in the future (such as hooking into some kind of filter or other future JUnit feature) your code will be able to leverage that.

The real purpose of the assert keyword in java is to be able to turn it off without runtime penalty. That doesn't apply to unit tests.

Upvotes: 113

Bruno D. Rodrigues
Bruno D. Rodrigues

Reputation: 400

I'd say use JUnit asserts in test cases, and use java's assert in the code. In other words, real code shall never have JUnit dependencies, as obvious, and if it's a test, it should use the JUnit variations of it, never the assert.

Upvotes: 11

starmer
starmer

Reputation: 2277

When a test fails you get more infomation.

assertEquals(1, 2); results in java.lang.AssertionError: expected:<1> but was:<2>

vs

assert(1 == 2); results in java.lang.AssertionError

you can get even more info if you add the message argument to assertEquals

Upvotes: 27

Dan Coates
Dan Coates

Reputation: 2012

This may not apply if you exclusively use stuff that's shiny and new, but assert was not introduced into Java until 1.4SE. Therefore, if you must work in an environment with older technology, you may lean towards JUnit for compatibility reasons.

Upvotes: 1

CheesePls
CheesePls

Reputation: 897

I would say if you are using JUnit you should use the JUnit assertions. assertTrue() is basically the same as assert, Otherwise why even use JUnit?

Upvotes: 0

Adamski
Adamski

Reputation: 54725

I prefer JUnit assertions as they offer a richer API than the built-in assert statement and, more importantly do not need to be explicitly enabled unlike assert, which requires the -ea JVM argument.

Upvotes: 30

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