JUnit4: assumeThat message is not printing - junit4

Question

How can I see the error messages of assumeThat in JUnit4?
This test passes but does not print anything. The reason is that to perform the test on read1, I require b to be true. Since b is false, the test does not apply.
boolean b = false;
byte[] read1 = null;
assumeThat("b shold be true to continue testing", b, is(true));
assertThat("read1 should not be null", read1, is(notNullValue()));
I have not found any kind of log with the assumeThat messages. My issue here is that I would like to know which tests passed but did not completed because assumption X failed. It would be nice if a message (for example similar to when an assertion fails) was still printed for the assumptions.
Strangely as it may seem, I haven't been able to find comments on this problem (including in the JUnit page). So there is a chance that I'm just doing something wrong or looking for messages in the wrong place. I'm using Eclipe.

Answer 1

If I understand you correctly, the
assertThat("read1 should not be null", read1, is(notNullValue()));
should only be executed if b == true, but it's not an error if b == false?
Then why don't you simply do:
if(b) {
assertThat("read1 should not be null", read1, is(notNullValue()));
} else {
log.warn("b == false, Test on read1 skipped");
}
? Or do you want to have a special test result state ("success-but-suspicious") if that happens?
Update: I just re-read the docs on Assume. It states that if an assumtion fails, the entire test is considered "not meaningful" and marked as "ignored". With small, focused tests that should usually give you all the info you need.
Update2: Just tried it with the JUnit 4.8 in Eclipse 4.2 I have on hand here. That just marks the test as successful. So I guess the JUnit runner in Eclipse might not support that feature correctly.

Answer 2

An error isn't printed because an assumption failure isn't an error. The assume methods are used to short-circuit tests that should not be run due to the value or state one or more objects (or primitives). Assumptions were designed for the Theories runner but they can be used in other runners as well.
One common usage of assumptions is when you have multiple test methods that need to perform some set of operations to get an object into a particular state before the actual test case logic can be performed.
Before assumptions, each test would get the object into a desired state, assert that it is in that state, then continue. For example, for a test of a stack, many tests require a non-empty stack, so you would create a stack, push an item, assert the stack is not empty, then do the rest of the test (pop an item, push another item, etc).
The problem comes if you do this pattern in multiple tests, and then a bug gets introduced that causes all of these tests to fail (for example, isEmpty() always returning true). When you run the tests you get so many failures that you don't know where to start.
So instead you have one test that verifies that if you push an item into an empty stack, isEmpy() returns false. Then any test that needs a non-empty stack does this:
Stack<Object> stack = new Stack<>();
stack.push(new Object());
assumeFalse(stack.isEmpty());
// Continue with the test methods
If you want an error message, you probably want to use an assertion.

Answer 3

Agreeing with the previous answer (by NamshubWriter).
However, if you really want (justifiably) to have a clear indication that the test was ignored because some assumption failed, you can do something like:
#Before
public void before() {
final String mandatoryPropKey = "system.mandatory-property-for-this-test";
final String mandatoryPropExpectedVal = "true";
try { // try/catch because the Assume failure won't print any message (by design)
Assume.assumeTrue("Assumed that the \"" + mandatoryPropKey + "\" system property is \"" + mandatoryPropExpectedVal + "\".", Boolean.valueOf(System.getProperty(mandatoryPropKey, mandatoryPropExpectedVal)));
} catch (AssumptionViolatedException ave) {
logger.warn("Not executing this test because this assumption failed: {}", ave.getMessage());
throw ave;
}
}