Add a function that compares JSON dictionaries.

[mplorentz]

We should include a function that can compare to [String: Any] JSON-like dictionaries for equality. This is a very common need for unit testing network code.

[mplorentz]

Here's some code I wrote for another project that might be a useful starting point. It doesn't give a very nice error message if two values don't match up, but it does the assertion.

// MARK: - JSON Assertions

// This file contains some assertions that are helpful for asserting that JSON objects are equal without respect for
// key order.

/// Asserts that the two given sets of JSON data are equal and not nil. Will call `XCTFail()` if they are not.
///
/// - parameter data1: A `Data` that contains a utf8 encoded JSON.
/// - parameter data2: A `Data` that contains a utf8 encoded JSON.
func XCTAssertEqualJSONData(_ data1: Data?, _ data2: Data?) {
    // Guard against nil arguments
    guard let data1 = data1 else { XCTFail("first argument is nil"); return }
    guard let data2 = data2 else { XCTFail("second argument is nil"); return }

    // Try to decode to a Dictionary
    guard let jsonDict1 = try? JSONSerialization.jsonObject(with: data1, options: []) as? [String: AnyObject] else {
        XCTFail("data1 is not a valid JSON Dictionary.")
        return
    }

    guard let jsonDict2 = try? JSONSerialization.jsonObject(with: data2, options: []) as? [String: AnyObject] else {
        XCTFail("data2 is not a valid JSON Dictionary.")
        return
    }

    XCTAssertEqual(jsonDict1, jsonDict2)
}

/// Asserts that the two given JSON dictionaries are equal and not nil. Will call `XCTFail()` if they are not.
///
/// - parameter dictionary1: A `[String: AnyObject]?` representing a JSON object.
/// - parameter dictionary2: A `[String: AnyObject]?` representing a JSON object.
func XCTAssertEqual(_ dictionary1: [String: AnyObject]?, _ dictionary2: [String: AnyObject]?) {
    // Guard against nil arguments
    guard let dictionary1 = dictionary1 else { XCTFail("first argument is nil"); return }
    guard let dictionary2 = dictionary2 else { XCTFail("second argument is nil"); return }

    /// Assert that keys are equal
    XCTAssert(NSDictionary(dictionary: dictionary1).isEqual(to: dictionary2))
}