Not proper "oneOf" handling

[antonCPU]

{
    "oneOf": [
        {
            "type": "object",
            "properties": {
                "key": {
                    "type": "string"
                },
                "test1": {
                    "type": "string"
                }
            },
            "required": ["key", "test1"]
        },
        {
            "type": "object",
            "properties": {
                "key": {
                    "type": "string"
                },
                "test2": {
                    "type": "string"
                }
            },
            "required": ["key", "test2"]
        }
    ]
}

This schema will pass for:

{
     "test2" : "ok"
}

Because of array_unique() usage in JsonSchema\Constraints\Constraint::getErrors().
When the second schema will be checked a list of errors will contain "key" and "test1" errors. During checking will be added another error with "key" required, but array_unique() will erase it, so this schema will pass a criteria in JsonSchema\Constraints\Underfined::validateOfProperties() as a result.

[jojo1981]

Tested this issue with version: 2.0.0 and it works like supposed.

[
    {
        "property": "key",
        "message": "The property key is required",
        "constraint": "required"
    },
    {
        "property": "test1",
        "message": "The property test1 is required",
        "constraint": "required"
    },
    {
        "property": "",
        "message": "Failed to match exactly one schema",
        "constraint": "oneOf"
    }
]

@bighappyface I think this one can also be closed?

[bighappyface]

@jojo1981 thanks!