Allow suppressing the "expected" and the "actual" values in failure messages, particularly in RecursiveComparisonAssert

[tslmy]

Feature summary

In RecursiveComparisonAssert, the method isEqualTo is currently hard-coded to employ the ErrorMessageFactory ShouldBeEqualByComparingFieldByFieldRecursively:

assertj/assertj-core/src/main/java/org/assertj/core/api/RecursiveComparisonAssert.java

Line 15 in 4b280c4

import static org.assertj.core.error.ShouldBeEqualByComparingFieldByFieldRecursively.shouldBeEqualByComparingFieldByFieldRecursively;

assertj/assertj-core/src/main/java/org/assertj/core/api/RecursiveComparisonAssert.java

Line 157 in 4b280c4

if (!differences.isEmpty()) throw objects.getFailures().failure(info, shouldBeEqualByComparingFieldByFieldRecursively(actual,

In practice, users may be interested in customizing the error message.

One real use case is when comparing two large JSON files (represented by a nested object of Maps and Lists). In such scenarios, due to the default message always printing the whole "actual" and "expected" values...

assertj/assertj-core/src/main/java/org/assertj/core/error/ShouldBeEqualByComparingFieldByFieldRecursively.java

Line 37 in 4b280c4

"Expecting actual:%n" +

... the assertion failure message may flood the terminal buffer, resulting in unreadable outputs, which goes against AssertJ's philosophy of being ergonomic.

Example

assertThat(got)
    .usingRecursiveComparison()
    .isEqualTo(want);

This is what I see in IntelliJ IDEA -- Note how the message has been automatically shortened (with <...>), so I can't actually read what's wrong:

java.lang.AssertionError: 
Expecting actual:
  {"eee"="ffff"},
    {"dddd"="cccc", "bbbb"="aaaa"<...>ompared with the following comparators:
  - java.lang.Double -> org.assertj.core.api.recursive.comparison.RecursiveComparisonConfiguration$$Lambda$2878/0x0000000802a995a0@4bda79d2
  - java.lang.Float -> org.assertj.core.api.recursive.comparison.RecursiveComparisonConfiguration$$Lambda$2878/0x0000000802a995a0@2a22ff7b
  - java.lang.Integer -> org.assertj.core.api.recursive.comparison.RecursiveComparisonConfiguration$$Lambda$2878/0x0000000802a995a0@122b5f62
  - java.lang.Long -> org.assertj.core.api.recursive.comparison.RecursiveComparisonConfiguration$$Lambda$2878/0x0000000802a995a0@8120f15
  - java.nio.file.Path -> lexicographic comparator (Path natural order)
- actual and expected objects and their fields were compared field by field recursively even if they were not of the same type, this allows for example to compare a Person to a PersonDto (call strictTypeChecking(true) to change that behavior).
- the introspection strategy used was: DefaultRecursiveComparisonIntrospectionStrategy

My terminal emulator also can't handle this much output, resulting in me only able to see the last few lines of this message.

When running this assertion in a CI environment, whenever it fails, the console log page would be unable to render properly in my browser due to the sheer amount of text.

[joel-costigliola]

@tslmy if you are comparing JSON document, have you tried using https://github.com/lukas-krecan/JsonUnit ?

That might give you a more precise error.

[joel-costigliola]

You can also use overridingErrorMessage to change the error message as you like, see the corresponding javadoc.

[tslmy]

Thanks for the recommendation. Let me try tomorrow. I wasn't aware of that library.