Bug: nested arrays cause array to string conversion in Subset

[Danny-Smart]

If an expectation fails a count check, Mockery converts argument matchers into strings in order to display the expectation in the assertion failure message. When this is done to the Subset matcher when using a nested subset of arrays, casting to a string causes an "Array to string conversion" error

public function testSubsetError()
{
  $expected = [
    "foo" => [
      "bar" => "baz"
    ]
  ];

  $mock = \Mockery::mock(\Exception::class);
  $mock->shouldReceive("getMessage")->with(\Mockery::subset($expected))->once();
}

Results in :

There was 1 error:

1) tests\ExampleTest::testSubsetError()
Array to string conversion

/project/path/mockery/library/Mockery/Matcher/Subset.php:87

[ghostwriter]

Resolved via #1253