Throwable assertion support for hasMessageNormalizingNewlines(String)

[armandino]

I propose adding hasMessageNormalizingNewlines(String) method for asserting Throwable messages.

Currently, this can be done using workarounds, e.g.

Throwable ex = catchThrowable(() -> someMethod());
      
assertThat(ex.getMessage()).isEqualToNormalizingNewlines("multiline\nmessage");

Check List:

• Fixes #??? (ignore if not applicable)
• Unit tests : YES
• Javadoc with a code example (on API only) : YES
• PR meets the contributing guidelines

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[joel-costigliola]

@armandino sorry for the late reply, you already have a way to do that (nicely I think) with message():

assertThat(ex).message().isEqualToNormalizingNewlines("multiline\nmessage");

[armandino]

@joel-costigliola thank you for the suggestion. That definitely works. The only downside is that it requires getting an instance of the thrown exception, as in my snippet above.

I usually use assertThatThrownBy:

assertThatThrownBy(() -> someMethod())
    .isInstanceOf(SomeException.class)
    .hasMessage("...");

but this doesn't does not support the following usage:

assertThatThrownBy(() -> someMethod())
    .isInstanceOf(SomeException.class)
    .hasMessageNormalizingNewlines("...");  // would be nice to have

With the introduction of text blocks (https://openjdk.org/jeps/378), hasMessageNormalizingNewlines() would be a useful addition, unless there's another AssertJ APi that supports doing something like this that I'm not aware of.

[joel-costigliola]

@armandino the following snippet works because assertThatThrownBy returns AbstractThrowableAssert which exposes message(), that should work for you too, right ?

assertThatThrownBy(() -> {})
   .isInstanceOf(Exception.class)
   .message()
   .isEqualToNormalizingNewlines("...");

[armandino]

@joel-costigliola yes, that does work. I wasn't aware the message() method is exposed there. Thanks again! I'll close the PR.