Support for IntelliJ diffing

[wafisher]

When I use JUnit's Assert library, IntelliJ will provide a link in the console to a window where I can compare expected vs. actual results. Apparently this is from code like this. Are there any plans to support this with truth?

Thanks!

[jbduncan]

@wafisher I'm not on the Truth team, and I could very well be wrong about this as I'm going just by memory here, but I thought Truth was already supported by IntelliJ in this way.

Can you provide a screenshot proving that it doesn't happen for a typical Truth assertion?

[wafisher]

Unfortunately, all I get is:

java.lang.AssertionError: Not true that <[1483732224, 1483733032, 1483733309, 1483733459, 1483733969]> is equal to <[1483732224, 1483733032, 1483733309, 1483733459, 1483733969]> (although their toString() representations are the same)

	at com.bowerylabs.position.query.MTAPositionGeneratorTest.getPositions(MTAPositionGeneratorTest.kt:64)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
	at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
	at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
	at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
	at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
	at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
	at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
	at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
	at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
	at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
	at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
	at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
	at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
	at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:51)
	at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:237)
	at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at com.intellij.rt.execution.application.AppMain.main(AppMain.java:147)
Caused by: java.lang.AssertionError: Not true that <[1483732224, 1483733032, 1483733309, 1483733459, 1483733969]> is equal to <[1483732224, 1483733032, 1483733309, 1483733459, 1483733969]> (although their toString() representations are the same)
	at com.google.common.truth.FailureStrategy.fail(FailureStrategy.java:28)
	at com.google.common.truth.FailureStrategy.fail(FailureStrategy.java:22)
	at com.google.common.truth.Subject.failComparingToStrings(Subject.java:335)
	at com.google.common.truth.Subject.doEqualCheck(Subject.java:127)
	at com.google.common.truth.Subject.isEqualTo(Subject.java:104)
	... 28 more

[jbduncan]

@wafisher Yes, I think you're actually right!

I recently encountered in one of my personal projects that IntelliJ didn't give a <Click to see difference> link when a Truth-based assertion in one of my tests failed.

It's not clear to me if there is anything Truth can do about this without resorting to a hack of some kind...

[dinesh707]

Other than the original question, I have some doubt about the error message (as shown in stack).

java.lang.AssertionError: Not true that
<[1483732224, 1483733032, 1483733309, 1483733459, 1483733969]> is equal to
<[1483732224, 1483733032, 1483733309, 1483733459, 1483733969]> (although their toString() representations are the same)

@jbduncan, what was you testing ?, and how could this end up in a situation like this (where all numbers looks same and still assertion error). In your original screenshot you have different values.

[jbduncan]

Hi @dinesh707, I think you have the wrong end of the stick; you'll have to ask @wafisher, as he's the OP of the issue, not me. :)

[wafisher]

Oh just bad copying/pasting I think the last one should be ...970.

[dimo414]

The issue is that only certain assertions get this diffing treatment - anything that calls .failComparing() should trigger that same <Click to see difference> message in IntelliJ (at least, I've seen it before), but it's generally limited to string comparisons, not arbitrary failures. As you can see in the stack trace Subject.isEqualTo() ends up just calling .fail(), since there's not necessarily a reasonable diff to generate for arbitrary objects.

Generally an easy workaround would be to add an assertion about the objects' .toString() representations:

 assertThat(foo.toString()).isEqualTo(bar.toString());

Though in this case I'm aware this wouldn't work since their .toString() is equivalent.

Other assertions, like IterableSubject.containsExactly(), will report the different elements of the iterable, though I don't imagine IntelliJ will display that nicely. I'm not sure if there's a good way to support that case.

[cpovirk]

As of Truth 0.41, we are throwing ComparisonFailure for most equality assertions. I believe that should be enough for IntelliJ. Let us know if we're missing cases.

[theapache64]

@dimo414 @cpovirk
I tried with the below

 assertThat(foo.toString()).isEqualTo(bar.toString());

but still, IntelliJ doesn't show the Click to see difference action. I am using Truth 1.1.3. Any idea?

[cpovirk]

@theapache64, do you know if you have JUnit 4 on the classpath? Truth currently needs JUnit 4 to produce the "Click to see difference" output. (We'd like to produce it even without JUnit 4 on the classpath, but we haven't done that work yet.)

Truth pulls in JUnit 4 as a transitive Maven dependency by default, but some people exclude it.

(There's some history in #333, but I should summarize it someday.)

If you don't have JUnit 4 on the classpath, are you writing JUnit 5 tests?