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How to trick Android NFC tag object for unit testing

I am currently working on an Android project that needs NFC integration. Now I want to write some (j) unit tests to find out if the application can receive NFC intentions (in particular, ACTION_TECH_DISCOVERED ) and put this tag (in NfcAdapter.EXTRA_TAG ) on the bus system. However, to my surprise, I cannot create a Tag instance or layout. Can someone explain to me how I can (single) test?

At this point, I would even take the form of integration testing, the process:

  • NFC Intent Detection
  • Get Tag Object
  • Place it on a bus wrapped in a CardDetectedEvent .

I have an NFC-enabled phone and several cards for testing.

Android SDK Version: 19
Used libraries: robolectric, junit and mockito

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It is possible to instantiate a mock tag using reflection (note that this is not part of the public Android SDK, so it may not work for future versions of Android).

  • Get createMockTag() method, although reflection:

     Class tagClass = Tag.class; Method createMockTagMethod = tagClass.getMethod("createMockTag", byte[].class, int[].class, Bundle[].class);

  • Define some constants for preparing the mock tag instance:

     final int TECH_NFC_A = 1; final String EXTRA_NFC_A_SAK = "sak"; // short (SAK byte value) final String EXTRA_NFC_A_ATQA = "atqa"; // byte[2] (ATQA value) final int TECH_NFC_B = 2; final String EXTRA_NFC_B_APPDATA = "appdata"; // byte[] (Application Data bytes from ATQB/SENSB_RES) final String EXTRA_NFC_B_PROTINFO = "protinfo"; // byte[] (Protocol Info bytes from ATQB/SENSB_RES) final int TECH_ISO_DEP = 3; final String EXTRA_ISO_DEP_HI_LAYER_RESP = "hiresp"; // byte[] (null for NfcA) final String EXTRA_ISO_DEP_HIST_BYTES = "histbytes"; // byte[] (null for NfcB) final int TECH_NFC_F = 4; final String EXTRA_NFC_F_SC = "systemcode"; // byte[] (system code) final String EXTRA_NFC_F_PMM = "pmm"; // byte[] (manufacturer bytes) final int TECH_NFC_V = 5; final String EXTRA_NFC_V_RESP_FLAGS = "respflags"; // byte (Response Flag) final String EXTRA_NFC_V_DSFID = "dsfid"; // byte (DSF ID) final int TECH_NDEF = 6; final String EXTRA_NDEF_MSG = "ndefmsg"; // NdefMessage (Parcelable) final String EXTRA_NDEF_MAXLENGTH = "ndefmaxlength"; // int (result for getMaxSize()) final String EXTRA_NDEF_CARDSTATE = "ndefcardstate"; // int (1: read-only, 2: read/write, 3: unknown) final String EXTRA_NDEF_TYPE = "ndeftype"; // int (1: T1T, 2: T2T, 3: T3T, 4: T4T, 101: MF Classic, 102: ICODE) final int TECH_NDEF_FORMATABLE = 7; final int TECH_MIFARE_CLASSIC = 8; final int TECH_MIFARE_ULTRALIGHT = 9; final String EXTRA_MIFARE_ULTRALIGHT_IS_UL_C = "isulc"; // boolean (true: Ultralight C) final int TECH_NFC_BARCODE = 10; final String EXTRA_NFC_BARCODE_BARCODE_TYPE = "barcodetype"; // int (1: Kovio/ThinFilm)

  • Create a technical add-on package for your tag type. For example, for an NFC-A tag with an NDEF message:

     Bundle nfcaBundle = new Bundle(); nfcaBundle.putByteArray(EXTRA_NFC_A_ATQA, new byte[]{ (byte)0x44, (byte)0x00 }); //ATQA for Type 2 tag nfcaBundle.putShort(EXTRA_NFC_A_SAK , (short)0x00); //SAK for Type 2 tag Bundle ndefBundle = new Bundle(); ndefBundle.putInt(EXTRA_NDEF_MAXLENGTH, 48); // maximum message length: 48 bytes ndefBundle.putInt(EXTRA_NDEF_CARDSTATE, 1); // read-only ndefBundle.putInt(EXTRA_NDEF_TYPE, 2); // Type 2 tag NdefMessage myNdefMessage = ...; // create an NDEF message ndefBundle.putParcelable(EXTRA_NDEF_MSG, myNdefMessage); // add an NDEF message

  • Prepare a collision avoidance identifier / UID for your tag (see Tag.getId() method). For instance. 7-byte UID for Type 2 tag:

     byte[] tagId = new byte[] { (byte)0x3F, (byte)0x12, (byte)0x34, (byte)0x56, (byte)0x78, (byte)0x90, (byte)0xAB };

  • Then you can create an instance of the mock tag by calling the createMockTag() method

     Tag mockTag = (Tag)createMockTagMethod.invoke(null, tagId, // tag UID/anti-collision identifier (see Tag.getId() method) new int[] { TECH_NFC_A, TECH_NDEF }, // tech-list new Bundle[] { nfcaBundle, ndefBundle }); // array of tech-extra bundles, each entry maps to an entry in the tech-list

Once you have created this mock tag object, you can send it as part of your NFC discovery intent. For instance. for the purpose of TECH_DISCOVERED :

 Intent techIntent = new Intent(NfcAdapter.ACTION_TECH_DISCOVERED); techIntent.putExtra(NfcAdapter.EXTRA_ID, tagId); techIntent.putExtra(NfcAdapter.EXTRA_TAG, mockTag); techIntent.putExtra(NfcAdapter.EXTRA_NDEF_MESSAGES, new NdefMessage[]{ myNdefMessage }); // optionally add an NDEF message

You can then submit this intention to your activity:

 techIntent.setComponent(...); // or equivalent to optionally set an explicit receiver startActivity(techIntent);

The receiver can even use the mock tag object to retrieve instances of technology classes. However, any method that requires I / O will fail.

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I don’t think it’s possible to mock these intentions, since they are launched by NFCService and without system permissions it is impossible to launch these intentions, and currently there is no support in the Android environment for falsifying nfc tags.

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