assertArg example in JavaDoc should report multiple failures at once

[rkrisztian]

I've seen that Mockito adds assertArg in version 5.3.0 (#2285):

verify(otherServiceMock).doStuff(assertArg(param -> {
    assertThat(param.getField1()).isEqualTo("value1");
    assertThat(param.getField2()).isEqualTo("value2");
}));

That is nice, I appreciate a lot, but my problem is, and this is often overlooked: we should report multiple failures at once (where assertions are independent of each other). To give a better example we can:

• Use JUnit's assertAll
• Use AssertJ's assertSoftly
• Or use AssertJ's tuple and/or extracting (if lists are involved)

Example:

verify(otherServiceMock).doStuff(assertArg(param -> {
    assertThat(​tuple(param.getField1(), param.getField2())​)
            .isEqualTo(​tuple("value1", "value2"));
}));

Or whatever code style you find more readable.

Sadly, several frameworks/libraries get it wrong as well:

• REST Assured
• Spring MockMvcTest before adding andExpectAll in Spring Framework v5.3.10
• Several JavaScript/TypeScript testing tools
• (there could be more...)

[scordio]

Mockito has no way to catch multiple failures thrown by the Consumer of assertArg. If such behavior is desired, the writer of the Consumer should take care of it, e.g.:

verify(otherServiceMock).doStuff(assertArg(param -> 
    assertThat(param).satisfies(
        p -> assertThat(p.getField1()).isEqualTo("value1"),
        p -> assertThat(p.getField2()).isEqualTo("value2")
)));

(manually written, beware of typos)

To support this use case, Mockito could add a new assertArg(Consumer...) which behaves like AssertJ satisfies and would allow to write something like:

verify(otherServiceMock).doStuff(assertArg(
    param -> assertThat(param.getField1()).isEqualTo("value1"),
    param -> assertThat(param.getField2()).isEqualTo("value2")
));

Happy to raise a PR if the Mockito team likes the idea.