Note that only this line is actually being tested – only the value last of the last statement is returned and == is just a pure function here, not an assertion. You could try joining all the conditions with && to test the first 2 equalities too.

@Vilkina

This means that instead of writing:

Chunk(1, 2, 3).zipAllWith(Chunk(3, 2, 1))(_ => 0, _ => 0)(_ + _) == Chunk(4, 4, 4)
    Chunk(1, 2, 3).zipAllWith(Chunk(3, 2))(_ => 0, _ => 0)(_ + _) == Chunk(4, 4, 0)
    Chunk(1, 2).zipAllWith(Chunk(3, 2, 1))(_ => 0, _ => 0)(_ + _) == Chunk(4, 4, 0)

You should instead write:

(Chunk(1, 2, 3).zipAllWith(Chunk(3, 2, 1))(_ => 0, _ => 0)(_ + _) == Chunk(4, 4, 4)) &&
(Chunk(1, 2, 3).zipAllWith(Chunk(3, 2))(_ => 0, _ => 0)(_ + _) == Chunk(4, 4, 0)) &&
(Chunk(1, 2).zipAllWith(Chunk(3, 2, 1))(_ => 0, _ => 0)(_ + _) == Chunk(4, 4, 0))

The reason is that in Specs2, the line Chunk(...) == Chunk(..) constructs a value. So you have 3 lines of code, each constructing a value:

<construct value 1>
<construct value 2>
<construct value 3>

But in Scala, when you define a method like so:

def method = {
  <construct value 1>
  <construct value 2>
  <construct value 3>
}

Then the first two values (1 and 2, in this example), will be "thrown away". The method will return only the final value (3).

We want to return a test value that combines all them together. We want all tests to pass, so we use the "and" operator &&, which can take two test results and return another test result, which will succeed only if both tests succeeded.