The nfc-helpers.js requires an implementation of the WebNFCTest interfaces, which should emulate platform Web NFC backends.

The WebNFCTest interface is defined as:

  class NFCTestChromium {
    initialize();  // Sets up the testing environment.
    async reset(); // Frees the resources.
    getMockNFC(); // Returns `MockNFC` interface.
  };

  class MockNFC {
    setHWStatus(number status); // Sets the hardware status.
    setReadingMessage(NDEFMessageInit message); // Sets message that is used to deliver NFC reading updates.
    setPendingPushCompleted(boolean result); // Sets if the pending push is completed.
    setPushShouldTimeout(boolean result); // Sets flag to trigger the pending push to timeout.
    pushedMessage(); // Gets the pushed `NDEFMessageSource`.
    pushOptions(); // Gets the pushed `NFCPushOptions`.
  };

The Chromium implementation of the WebNFCTest interface is located in nfc-mock.js.

Other browser vendors should provide their own implementations of the WebNFCTest interfaces.